# 4.4 Understand slope of a line  (Page 7/14)

 Page 7 / 14

In the following exercises, find the slope of each line.

$y=3$

0

$y=1$

$x=4$

undefined

$x=2$

$y=-2$

0

$y=-3$

$x=-5$

undefined

$x=-4$

Use the Slope Formula to find the Slope of a Line between Two Points

In the following exercises, use the slope formula to find the slope of the line between each pair of points.

$\left(1,4\right),\left(3,9\right)$

$\frac{5}{2}$

$\left(2,3\right),\left(5,7\right)$

$\left(0,3\right),\left(4,6\right)$

$\frac{3}{4}$

$\left(0,1\right),\left(5,4\right)$

$\left(2,5\right),\left(4,0\right)$

$-\frac{5}{2}$

$\left(3,6\right),\left(8,0\right)$

$\left(-3,3\right),\left(4,-5\right)$

$-\frac{8}{7}$

$\left(-2,4\right),\left(3,-1\right)$

$\left(-1,-2\right),\left(2,5\right)$

$\frac{7}{3}$

$\left(-2,-1\right),\left(6,5\right)$

$\left(4,-5\right),\left(1,-2\right)$

$-1$

$\left(3,-6\right),\left(2,-2\right)$

Graph a Line Given a Point and the Slope

In the following exercises, graph each line with the given point and slope.

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

$\left(1,-1\right)$ ; $m=\frac{2}{3}$

$\left(2,5\right)$ ; $m=-\frac{1}{3}$

$\left(1,4\right)$ ; $m=-\frac{1}{2}$

$\left(-3,4\right)$ ; $m=-\frac{3}{2}$

$\left(-2,5\right)$ ; $m=-\frac{5}{4}$

$\left(-1,-4\right)$ ; $m=\frac{4}{3}$

$\left(-3,-5\right)$ ; $m=\frac{3}{2}$

y -intercept 3; $m=-\frac{2}{5}$

y -intercept 5; $m=-\frac{4}{3}$

x -intercept $-2$ ; $m=\frac{3}{4}$

x -intercept $-1$ ; $m=\frac{1}{5}$

$\left(-3,3\right)$ ; $m=2$

$\left(-4,2\right)$ ; $m=4$

$\left(1,5\right)$ ; $m=-3$

$\left(2,3\right)$ ; $m=-1$

## Everyday math

Slope of a roof. An easy way to determine the slope of a roof is to set one end of a 12 inch level on the roof surface and hold it level. Then take a tape measure or ruler and measure from the other end of the level down to the roof surface. This will give you the slope of the roof. Builders, sometimes, refer to this as pitch and state it as an “ $x$ 12 pitch” meaning $\frac{x}{12}$ , where $x$ is the measurement from the roof to the level—the rise. It is also sometimes stated as an “ $x$ -in-12 pitch”.

1. What is the slope of the roof in this picture?
2. What is the pitch in construction terms?

$\frac{1}{3}$ 4 12 pitch or 4-in-12 pitch

The slope of the roof shown here is measured with a 12” level and a ruler. What is the slope of this roof?

$\frac{3}{50}$ ; rise = 3, run = 50

Highway grade. A local road rises 2 feet for every 50 feet of highway.

What is the slope of the highway?
The grade of a highway is its slope expressed as a percent. What is the grade of this highway?

Wheelchair ramp. The rules for wheelchair ramps require a maximum 1-inch rise for a 12-inch run.

How long must the ramp be to accommodate a 24-inch rise to the door?
Create a model of this ramp.

288 inches (24 feet)  Models will vary.

Wheelchair ramp. A 1-inch rise for a 16-inch run makes it easier for the wheelchair rider to ascend a ramp.

How long must a ramp be to easily accommodate a 24-inch rise to the door?
Create a model of this ramp.

## Writing exercises

What does the sign of the slope tell you about a line?

When the slope is a positive number the line goes up from left to right. When the slope is a negative number the line goes down from left to right.

How does the graph of a line with slope $m=\frac{1}{2}$ differ from the graph of a line with slope $m=2$ ?

Why is the slope of a vertical line “undefined”?

A vertical line has 0 run and since division by 0 is undefined the slope is undefined.

## Self check

After completing the exercises, use this checklist to evaluate your mastery of the objectives of this section.

On a scale of 1–10, how would you rate your mastery of this section in light of your responses on the checklist? How can you improve this?

He charges $125 per job. His monthly expenses are$1,600. How many jobs must he work in order to make a profit of at least $2,400? Alicia Reply at least 20 Ayla what are the steps? Alicia 6.4 jobs Grahame 32 Grahame what is algebra Azhar Reply repeated addition and subtraction of the order of operations. i love algebra I'm obsessed. Shemiah hi Krekar One-fourth of the candies in a bag of M&M’s are red. If there are 23 red candies, how many candies are in the bag? Leanna Reply rectangular field solutions Navin Reply What is this? Donna the proudact of 3x^3-5×^2+3 and 2x^2+5x-4 in z7[x]/ is anas Reply ? Choli a rock is thrown directly upward with an initial velocity of 96feet per second from a cliff 190 feet above a beach. The hight of tha rock above the beach after t second is given by the equation h=_16t^2+96t+190 Usman Stella bought a dinette set on sale for$725. The original price was $1,299. To the nearest tenth of a percent, what was the rate of discount? Manhwa Reply 44.19% Scott 40.22% Terence 44.2% Orlando I don't know Donna if you want the discounted price subtract$725 from $1299. then divide the answer by$1299. you get 0.4419... but as percent you get 44.19... but to the nearest tenth... round .19 to .2 and you get 44.2%
Orlando
you could also just divide $725/$1299 and then subtract it from 1. then you get the same answer.
Orlando
p mulripied-5 and add 30 to it
Tausif
Tausif
Can you explain further
p mulripied-5 and add to 30
Tausif
-5p+30?
Corey
p=-5+30
Jacob
How do you find divisible numbers without a calculator?
TAKE OFF THE LAST DIGIT AND MULTIPLY IT 9. SUBTRACT IT THE DIGITS YOU HAVE LEFT. IF THE ANSWER DIVIDES BY 13(OR IS ZERO), THEN YOUR ORIGINAL NUMBER WILL ALSO DIVIDE BY 13!IS DIVISIBLE BY 13
BAINAMA
When she graduates college, Linda will owe $43,000 in student loans. The interest rate on the federal loans is 4.5% and the rate on the private bank loans is 2%. The total interest she owes for one year was$1,585. What is the amount of each loan?
Sean took the bus from Seattle to Boise, a distance of 506 miles. If the trip took 7 2/3 hours, what was the speed of the bus?
66miles/hour
snigdha
How did you work it out?
Esther
s=mi/hr 2/3~0.67 s=506mi/7.67hr = ~66 mi/hr
Orlando
hello, I have algebra phobia. Subtracting negative numbers always seem to get me confused.
what do you need help in?
Felix
Heather
look at the numbers if they have different signs, it's like subtracting....but you keep the sign of the largest number...
Felix
for example.... -19 + 7.... different signs...subtract.... 12 keep the sign of the "largest" number 19 is bigger than 7.... 19 has the negative sign... Therefore, -12 is your answer...
Felix
—12
Thanks Felix.l also get confused with signs.
Esther
Thank you for this
Shatey
ty
Graham
think about it like you lost $19 (-19), then found$7(+7). Totally you lost just $12 (-12) Annushka I used to struggle a lot with negative numbers and math in general what I typically do is look at it in terms of money I have -$5 in my account I then take out 5 more dollars how much do I have in my account well-\$10 ... I also for a long time would draw it out on a number line to visualize it
Meg
practicing with smaller numbers to understand then working with larger numbers helps too and the song/rhyme same sign add and keep opposite signs subtract keep the sign of the bigger # then you'll be exact
Meg
Bruce drives his car for his job. The equation R=0.575m+42 models the relation between the amount in dollars, R, that he is reimbursed and the number of miles, m, he drives in one day. Find the amount Bruce is reimbursed on a day when he drives 220 miles
168.50=R
Heather
john is 5years older than wanjiru.the sum of their years is27years.what is the age of each
46
mustee
j 17 w 11
Joseph
john is 16. wanjiru is 11.
Felix
27-5=22 22÷2=11 11+5=16
Joyce
I don't see where the answers are.
Ed