# 3.1 Defining the derivative  (Page 6/10)

 Page 6 / 10

$f\left(x\right)=4x+7;{x}_{1}=2,{x}_{2}=5$

$4$

$f\left(x\right)=8x-3;{x}_{1}=-1,{x}_{2}=3$

$f\left(x\right)={x}^{2}+2x+1;{x}_{1}=3,{x}_{2}=3.5$

$8.5$

$f\left(x\right)=\text{−}{x}^{2}+x+2;{x}_{1}=0.5,{x}_{2}=1.5$

$f\left(x\right)=\frac{4}{3x-1};{x}_{1}=1,{x}_{2}=3$

$-\frac{3}{4}$

$f\left(x\right)=\frac{x-7}{2x+1};{x}_{1}=-2,{x}_{2}=0$

$f\left(x\right)=\sqrt{x};{x}_{1}=1,{x}_{2}=16$

$0.2$

$f\left(x\right)=\sqrt{x-9};{x}_{1}=10,{x}_{2}=13$

$f\left(x\right)={x}^{1\text{/}3}+1;{x}_{1}=0,{x}_{2}=8$

$0.25$

$f\left(x\right)=6{x}^{2\text{/}3}+2{x}^{1\text{/}3};{x}_{1}=1,{x}_{2}=27$

For the following functions,

1. use [link] to find the slope of the tangent line ${m}_{\text{tan}}={f}^{\prime }\left(a\right),$ and
2. find the equation of the tangent line to $f$ at $x=a.$

$f\left(x\right)=3-4x,a=2$

a. $-4$ b. $y=3-4x$

$f\left(x\right)=\frac{x}{5}+6,a=-1$

$f\left(x\right)={x}^{2}+x,a=1$

a. $3$ b. $y=3x-1$

$f\left(x\right)=1-x-{x}^{2},a=0$

$f\left(x\right)=\frac{7}{x},a=3$

a. $\frac{-7}{9}$ b. $y=\frac{-7}{9}x+\frac{14}{3}$

$f\left(x\right)=\sqrt{x+8},a=1$

$f\left(x\right)=2-3{x}^{2},a=-2$

a. $12$ b. $y=12x+14$

$f\left(x\right)=\frac{-3}{x-1},a=4$

$f\left(x\right)=\frac{2}{x+3},a=-4$

a. $-2$ b. $y=-2x-10$

$f\left(x\right)=\frac{3}{{x}^{2}},a=3$

For the following functions $y=f\left(x\right),$ find ${f}^{\prime }\left(a\right)$ using [link] .

$f\left(x\right)=5x+4,a=-1$

$5$

$f\left(x\right)=-7x+1,a=3$

$f\left(x\right)={x}^{2}+9x,a=2$

$13$

$f\left(x\right)=3{x}^{2}-x+2,a=1$

$f\left(x\right)=\sqrt{x},a=4$

$\frac{1}{4}$

$f\left(x\right)=\sqrt{x-2},a=6$

$f\left(x\right)=\frac{1}{x},a=2$

$-\frac{1}{4}$

$f\left(x\right)=\frac{1}{x-3},a=-1$

$f\left(x\right)=\frac{1}{{x}^{3}},a=1$

$-3$

$f\left(x\right)=\frac{1}{\sqrt{x}},a=4$

For the following exercises, given the function $y=f\left(x\right),$

1. find the slope of the secant line $PQ$ for each point $Q\left(x,f\left(x\right)\right)$ with $x$ value given in the table.
2. Use the answers from a. to estimate the value of the slope of the tangent line at $P.$
3. Use the answer from b. to find the equation of the tangent line to $f$ at point $P.$

[T] $f\left(x\right)={x}^{2}+3x+4,P\left(1,8\right)$ (Round to $6$ decimal places.)

x Slope ${m}_{PQ}$ x Slope ${m}_{PQ}$
1.1 (i) 0.9 (vii)
1.01 (ii) 0.99 (viii)
1.001 (iii) 0.999 (ix)
1.0001 (iv) 0.9999 (x)
1.00001 (v) 0.99999 (xi)
1.000001 (vi) 0.999999 (xii)

a. $\text{(i)}\phantom{\rule{0.2em}{0ex}}5.100000,$ $\text{(ii)}\phantom{\rule{0.2em}{0ex}}5.010000,$ $\text{(iii)}\phantom{\rule{0.2em}{0ex}}5.001000,$ $\text{(iv)}\phantom{\rule{0.2em}{0ex}}5.000100,$ $\text{(v)}\phantom{\rule{0.2em}{0ex}}5.000010,$ $\text{(vi)}\phantom{\rule{0.2em}{0ex}}5.000001,$ $\text{(vii)}\phantom{\rule{0.2em}{0ex}}4.900000,$ $\text{(viii)}\phantom{\rule{0.2em}{0ex}}4.990000,$ $\text{(ix)}\phantom{\rule{0.2em}{0ex}}4.999000,$ $\text{(x)}\phantom{\rule{0.2em}{0ex}}4.999900,$ $\text{(xi)}\phantom{\rule{0.2em}{0ex}}4.999990,$ $\text{(x)}\phantom{\rule{0.2em}{0ex}}4.999999$ b. ${m}_{\text{tan}}=5$ c. $y=5x+3$

[T] $f\left(x\right)=\frac{x+1}{{x}^{2}-1},P\left(0,-1\right)$

x Slope ${m}_{PQ}$ x Slope ${m}_{PQ}$
0.1 (i) $-0.1$ (vii)
0.01 (ii) $-0.01$ (viii)
0.001 (iii) $-0.001$ (ix)
0.0001 (iv) $-0.0001$ (x)
0.00001 (v) $-0.00001$ (xi)
0.000001 (vi) $-0.000001$ (xii)

[T] $f\left(x\right)=10{e}^{0.5x},P\left(0,10\right)$ (Round to $4$ decimal places.)

x Slope ${m}_{PQ}$
$-0.1$ (i)
$-0.01$ (ii)
$-0.001$ (iii)
$-0.0001$ (iv)
$-0.00001$ (v)
−0.000001 (vi)

a. $\text{(i)}\phantom{\rule{0.2em}{0ex}}4.8771,$ $\text{(ii)}\phantom{\rule{0.2em}{0ex}}4.9875\phantom{\rule{0.2em}{0ex}}\text{(iii)}\phantom{\rule{0.2em}{0ex}}4.9988,$ $\text{(iv)}\phantom{\rule{0.2em}{0ex}}4.9999,$ $\text{(v)}\phantom{\rule{0.2em}{0ex}}4.9999,$ $\text{(vi)}\phantom{\rule{0.2em}{0ex}}4.9999$ b. ${m}_{\text{tan}}=5$ c. $y=5x+10$

[T] $f\left(x\right)=\text{tan}\phantom{\rule{0.1em}{0ex}}\left(x\right),P\left(\pi ,0\right)$

x Slope ${m}_{PQ}$
3.1 (i)
3.14 (ii)
3.141 (iii)
3.1415 (iv)
3.14159 (v)
3.141592 (vi)

[T] For the following position functions $y=s\left(t\right),$ an object is moving along a straight line, where $t$ is in seconds and $s$ is in meters. Find

1. the simplified expression for the average velocity from $t=2$ to $t=2+h;$
2. the average velocity between $t=2$ and $t=2+h,$ where $\text{(i)}\phantom{\rule{0.2em}{0ex}}h=0.1,$ $\text{(ii)}\phantom{\rule{0.2em}{0ex}}h=0.01,$ $\text{(iii)}\phantom{\rule{0.2em}{0ex}}h=0.001,$ and $\text{(iv)}\phantom{\rule{0.2em}{0ex}}h=0.0001;$ and
3. use the answer from a. to estimate the instantaneous velocity at $t=2$ second.

$s\left(t\right)=\frac{1}{3}t+5$

a. $\frac{1}{3};$ b. $\text{(i)}\phantom{\rule{0.2em}{0ex}}0.\stackrel{–}{3}$ m/s, $\text{(ii)}\phantom{\rule{0.2em}{0ex}}0.\stackrel{–}{3}$ m/s, $\text{(iii)}\phantom{\rule{0.2em}{0ex}}0.\stackrel{–}{3}$ m/s, $\text{(iv)}\phantom{\rule{0.2em}{0ex}}0.\stackrel{–}{3}$ m/s; c. $0.\stackrel{–}{3}=\frac{1}{3}$ m/s

$s\left(t\right)={t}^{2}-2t$

$s\left(t\right)=2{t}^{3}+3$

a. $2\left({h}^{2}+6h+12\right);$ b. $\text{(i)}\phantom{\rule{0.2em}{0ex}}25.22$ m/s, $\text{(ii)}\phantom{\rule{0.2em}{0ex}}24.12$ m/s, $\text{(iii)}\phantom{\rule{0.2em}{0ex}}24.01$ m/s, $\text{(iv)}\phantom{\rule{0.2em}{0ex}}24$ m/s; c. $24$ m/s

$s\left(t\right)=\frac{16}{{t}^{2}}-\frac{4}{t}$

Use the following graph to evaluate a. ${f}^{\prime }\left(1\right)$ and b. ${f}^{\prime }\left(6\right).$ a. $1.25;$ b. $0.5$

Use the following graph to evaluate a. ${f}^{\prime }\left(-3\right)$ and b. ${f}^{\prime }\left(1.5\right).$ For the following exercises, use the limit definition of derivative to show that the derivative does not exist at $x=a$ for each of the given functions.

$f\left(x\right)={x}^{1\text{/}3},x=0$

$\underset{x\to {0}^{-}}{\text{lim}}\frac{{x}^{1\text{/}3}-0}{x-0}=\underset{x\to {0}^{-}}{\text{lim}}\frac{1}{{x}^{2\text{/}3}}=\infty$

$f\left(x\right)={x}^{2\text{/}3},x=0$

$f\left(x\right)=\left\{\begin{array}{c}1,x<1\\ x,x\ge 1\end{array},x=1$

$\underset{x\to {1}^{-}}{\text{lim}}\frac{1-1}{x-1}=0\ne 1=\underset{x\to {1}^{+}}{\text{lim}}\frac{x-1}{x-1}$

$f\left(x\right)=\frac{|x|}{x},x=0$

[T] The position in feet of a race car along a straight track after $t$ seconds is modeled by the function $s\left(t\right)=8{t}^{2}-\frac{1}{16}{t}^{3}.$

1. Find the average velocity of the vehicle over the following time intervals to four decimal places:
1. [4, 4.1]
2. [4, 4.01]
3. [4, 4.001]
4. [4, 4.0001]
2. Use a. to draw a conclusion about the instantaneous velocity of the vehicle at $t=4$ seconds.

a. $\text{(i)}\phantom{\rule{0.2em}{0ex}}61.7244$ ft/s, $\text{(ii)}\phantom{\rule{0.2em}{0ex}}61.0725$ ft/s $\text{(iii)}\phantom{\rule{0.2em}{0ex}}61.0072$ ft/s $\text{(iv)}\phantom{\rule{0.2em}{0ex}}61.0007$ ft/s b. At $4$ seconds the race car is traveling at a rate/velocity of $61$ ft/s.

[T] The distance in feet that a ball rolls down an incline is modeled by the function $s\left(t\right)=14{t}^{2},$ where t is seconds after the ball begins rolling.

1. Find the average velocity of the ball over the following time intervals:
1. [5, 5.1]
2. [5, 5.01]
3. [5, 5.001]
4. [5, 5.0001]
2. Use the answers from a. to draw a conclusion about the instantaneous velocity of the ball at $t=5$ seconds.

Two vehicles start out traveling side by side along a straight road. Their position functions, shown in the following graph, are given by $s=f\left(t\right)$ and $s=g\left(t\right),$ where $s$ is measured in feet and $t$ is measured in seconds. 1. Which vehicle has traveled farther at $t=2$ seconds?
2. What is the approximate velocity of each vehicle at $t=3$ seconds?
3. Which vehicle is traveling faster at $t=4$ seconds?
4. What is true about the positions of the vehicles at $t=4$ seconds?

a. The vehicle represented by $f\left(t\right),$ because it has traveled $2$ feet, whereas $g\left(t\right)$ has traveled $1$ foot. b. The velocity of $f\left(t\right)$ is constant at $1$ ft/s, while the velocity of $g\left(t\right)$ is approximately $2$ ft/s. c. The vehicle represented by $g\left(t\right),$ with a velocity of approximately $4$ ft/s. d. Both have traveled $4$ feet in $4$ seconds.

[T] The total cost $C\left(x\right),$ in hundreds of dollars, to produce $x$ jars of mayonnaise is given by $C\left(x\right)=0.000003{x}^{3}+4x+300.$

1. Calculate the average cost per jar over the following intervals:
1. [100, 100.1]
2. [100, 100.01]
3. [100, 100.001]
4. [100, 100.0001]
2. Use the answers from a. to estimate the average cost to produce $100$ jars of mayonnaise.

[T] For the function $f\left(x\right)={x}^{3}-2{x}^{2}-11x+12,$ do the following.

1. Use a graphing calculator to graph f in an appropriate viewing window.
2. Use the ZOOM feature on the calculator to approximate the two values of $x=a$ for which ${m}_{\text{tan}}={f}^{\prime }\left(a\right)=0.$

a. b. $a\approx -1.361,2.694$

[T] For the function $f\left(x\right)=\frac{x}{1+{x}^{2}},$ do the following.

1. Use a graphing calculator to graph $f$ in an appropriate viewing window.
2. Use the ZOOM feature on the calculator to approximate the values of $x=a$ for which ${m}_{\text{tan}}={f}^{\prime }\left(a\right)=0.$

Suppose that $N\left(x\right)$ computes the number of gallons of gas used by a vehicle traveling $x$ miles. Suppose the vehicle gets $30$ mpg.

1. Find a mathematical expression for $N\left(x\right).$
2. What is $N\left(100\text{)?}$ Explain the physical meaning.
3. What is ${N}^{\prime }\left(100\right)?$ Explain the physical meaning.

a. $N\left(x\right)=\frac{x}{30}$ b. $\sim 3.3$ gallons. When the vehicle travels $100$ miles, it has used $3.3$ gallons of gas. c. $\frac{1}{30}.$ The rate of gas consumption in gallons per mile that the vehicle is achieving after having traveled $100$ miles.

[T] For the function $f\left(x\right)={x}^{4}-5{x}^{2}+4,$ do the following.

1. Use a graphing calculator to graph $f$ in an appropriate viewing window.
2. Use the $\text{nDeriv}$ function, which numerically finds the derivative, on a graphing calculator to estimate ${f}^{\prime }\left(-2\right),{f}^{\prime }\left(-0.5\right),{f}^{\prime }\left(1.7\right),$ and ${f}^{\prime }\left(2.718\right).$

[T] For the function $f\left(x\right)=\frac{{x}^{2}}{{x}^{2}+1},$ do the following.

1. Use a graphing calculator to graph $f$ in an appropriate viewing window.
2. Use the $\text{nDeriv}$ function on a graphing calculator to find ${f}^{\prime }\left(-4\right),{f}^{\prime }\left(-2\right),{f}^{\prime }\left(2\right),$ and ${f}^{\prime }\left(4\right).$

a. b. $-0.028,-0.16,0.16,0.028$

#### Questions & Answers

find the domain and range of f(x)= 4x-7/x²-6x+8
Nick Reply
find the range of f(x)=(x+1)(x+4)
Jane Reply
-1, -4
Marcia
That's domain. The range is [-9/4,+infinity)
Jacob
If you're using calculus to find the range, you have to find the extrema through the first derivative test and then substitute the x-value for the extrema back into the original equation.
Jacob
Good morning,,, how are you
Harrieta Reply
d/dx{1/y - lny + X^3.Y^5}
mogomotsi Reply
How to identify domain and range
Umar Reply
hello
Akpevwe
He,,
Harrieta
hi
Dr
hello
velocity
I only talk to girls
Dr
women are smart then guys
Dr
Smarter
Adri
sorry
Dr
hi adri ana
Dr
:(
Shun
was up
Dr
hello
Adarsh
is it chatting app?.. I do not see any calculus here. lol
Adarsh
Find the arc length of the graph of f(x) = In (sinx) on the interval [Π/4, Π/2].
mukul Reply
Sand falling freely from a lorry form a conical shape whose height is always equal to one-third the radius of the base. a. How fast is the volume increasing when the radius of the base is (1m) and increasing at the rate of 1/4cm/sec Pls help me solve
ade
show that lim f(x) + lim g(x)=m+l
BARNABAS Reply
list the basic elementary differentials
Chio Reply
Differentiation and integration
Okikiola Reply
yes
Damien
proper definition of derivative
Syed Reply
the maximum rate of change of one variable with respect to another variable
Amdad
terms of an AP is 1/v and the vth term is 1/u show that the sum of uv terms is 1/2(uv+1)
Inembo Reply
what is calculus?
BISWAJIT Reply
calculus is math that studies the change in math, such as the rate and distance,
Tamarcus
what are the topics in calculus
Augustine
what is limit of a function?
Geoffrey Reply
what is x and how x=9.1 take?
Pravin Reply
what is f(x)
Inembo Reply
the function at x
Marc
also known as the y value so I could say y=2x or f(x)= 2x same thing just using functional notation your next question is what is dependent and independent variables. I am Dyslexic but know math and which is which confuses me. but one can vary the x value while y depends on which x you use. also
Marc
up domain and range
Marc
enjoy your work and good luck
Marc
I actually wanted to ask another questions on sets if u dont mind please?
Inembo
I have so many questions on set and I really love dis app I never believed u would reply
Inembo
Hmm go ahead and ask you got me curious too much conversation here
Adri
am sorry for disturbing I really want to know math that's why *I want to know the meaning of those symbols in sets* e.g n,U,A', etc pls I want to know it and how to solve its problems
Inembo
and how can i solve a question like dis *in a group of 40 students, 32 offer maths and 24 offer physics and 4 offer neither maths nor physics , how many offer both maths and physics*
Inembo
next questions what do dy mean by (A' n B^c)^c'
Inembo
The sets help you to define the function. The function is like a magic box where you put inside stuff(numbers or sets) and you get out the stuff but in different shapes (forms).
Adri
I dont understand what you wanna say by (A' n B^c)^c'
Adri
(A' n B (rise to the power of c)) all rise to the power of c
Inembo
Aaaahh
Adri
Ok so the set is formed by vectors and not numbers
Adri
A vector of length n
Adri
But you can make a set out of matrixes as well
Adri
I I don't even understand sets I wat to know d meaning of all d symbolsnon sets
Inembo
Wait what's your math level?
Adri
High-school?
Adri
yes
Inembo
am having big problem understanding sets more than other math topics
Inembo
So f:R->R means that the function takes real numbers and provides real numer. For ex. If f(x) =2x this means if you give to your function a real number like 2,it gives you also a real number 2times2=4
Adri
pls answer this question *in a group of 40 students, 32 offer maths and 24 offer physics and 4 offer neither maths nor physics , how many offer both maths and physics*
Inembo
If you have f:R^n->R^n you give to your function a vector of length n like (a1,a2,...an) where all a1,.. an are reals and gives you also a vector of length n... I don't know if i answering your question. Otherwise on YouTube you havr many videos where they explain it in a simple way
Adri
I would say 24
Adri
Offer both
Adri
Sorry 20
Adri
Actually you have 40 - 4 =36 who offer maths or physics or both.
Adri
I know its 20 but how to prove it
Inembo
You have 32+24=56who offer courses
Adri
56-36=20 who give both courses... I would say that
Adri
solution: In a question involving sets and Venn diagram, the sum of the members of set A + set B - the joint members of both set A and B + the members that are not in sets A or B = the total members of the set. In symbolic form n(A U B) = n(A) + n (B) - n (A and B) + n (A U B)'.
Mckenzie
In the case of sets A and B use the letters m and p to represent the sets and we have: n (M U P) = 40; n (M) = 24; n (P) = 32; n (M and P) = unknown; n (M U P)' = 4
Mckenzie
Now substitute the numerical values for the symbolic representation 40 = 24 + 32 - n(M and P) + 4 Now solve for the unknown using algebra: 40 = 24 + 32+ 4 - n(M and P) 40 = 60 - n(M and P) Add n(M and P), as well, subtract 40 from both sides of the equation to find the answer.
Mckenzie
40 - 40 + n(M and P) = 60 - 40 - n(M and P) + n(M and P) Solution: n(M and P) = 20
Mckenzie
thanks
Inembo
Simpler form: Add the sums of set M, set P and the complement of the union of sets M and P then subtract the number of students from the total.
Mckenzie
n(M and P) = (32 + 24 + 4) - 40 = 60 - 40 = 20
Mckenzie

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