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Evaluate: 17 k when k = 19 and k = −19 .

−2 36

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Evaluate: −5 b when b = 14 and b = −14 .

−19 9

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Evaluate: 2 x 2 + 3 x + 8 when x = 4 .

Solution

Substitute 4 for x . Use parentheses to show multiplication.

.
Substitute. .
Evaluate exponents. .
Multiply. .
Add. 52

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Evaluate: 3 x 2 2 x + 6 when x = −3 .

39

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Evaluate: 4 x 2 x 5 when x = −2 .

13

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Translate phrases to expressions with integers

Our earlier work translating English to algebra also applies to phrases that include both positive and negative numbers.

Translate and simplify: the sum of 8 and −12 , increased by 3.

Solution

the sum of 8 and −12 , increased by 3 Translate. [ 8 + ( −12 ) ] + 3 Simplify. Be careful not to confuse the brackets with an absolute value sign. ( −4 ) + 3 Add. −1

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Translate and simplify the sum of 9 and −16 , increased by 4.

( 9 + ( −16 ) ) + 4 3

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Translate and simplify the sum of −8 and −12 , increased by 7.

( −8 + ( −12 ) ) + 7 13

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When we first introduced the operation symbols, we saw that the expression may be read in several ways. They are listed in the chart below.

a b
a minus b
the difference of a and b
b subtracted from a
b less than a

Be careful to get a and b in the right order!

Translate and then simplify the difference of 13 and −21 subtract 24 from −19 .

Solution


  1. the difference of 13 and 21 Translate. 13 ( −21 ) Simplify. 34


  2. subtract 24 from 19 Translate. Remember, “subtract b from a means a b . 19 24 Simplify. −43
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Translate and simplify the difference of 14 and −23 subtract 21 from −17 .

14 ( −23 ) ; 37 −17 21 ; 38

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Translate and simplify the difference of 11 and −19 subtract 18 from −11 .

11 ( −19 ) ; 30 −11 18 ; 29

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Once again, our prior work translating English to algebra transfers to phrases that include both multiplying and dividing integers. Remember that the key word for multiplication is “ product ” and for division is “ quotient .”

Translate to an algebraic expression and simplify if possible: the product of −2 and 14.

Solution

the product of −2 and 14 Translate. ( −2 ) ( 14 ) Simplify. −28

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Translate to an algebraic expression and simplify if possible: the product of −5 and 12.

−5 ( 12 ) ; 60

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Translate to an algebraic expression and simplify if possible: the product of 8 and −13 .

−8 ( 13 ) ; 104

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Translate to an algebraic expression and simplify if possible: the quotient of −56 and −7 .

Solution

the quotient of −56 and −7 Translate. −56 ÷ ( −7 ) Simplify. 8

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Translate to an algebraic expression and simplify if possible: the quotient of −63 and −9 .

−63 ÷ ( −9 ) ; 7

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Translate to an algebraic expression and simplify if possible: the quotient of −72 and −9 .

−72 ÷ ( −9 ) ; 8

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Use integers in applications

We’ll outline a plan to solve applications. It’s hard to find something if we don’t know what we’re looking for or what to call it! So when we solve an application, we first need to determine what the problem is asking us to find. Then we’ll write a phrase that gives the information to find it. We’ll translate the phrase into an expression and then simplify the expression to get the answer. Finally, we summarize the answer in a sentence to make sure it makes sense.

How to apply a strategy to solve applications with integers

The temperature in Urbana, Illinois one morning was 11 degrees. By mid-afternoon, the temperature had dropped to −9 degrees. What was the difference of the morning and afternoon temperatures?

Solution

This is a table with two columns. The left column includes steps to solve the problem. The right column includes the math to solve the problem. In the first row, the left column says “Step 1. Read the problem. Make sure all the words and ideas are understood.” The right column is blank. In the second row, the left column says “Step 2. Identify what we are asked to find”. The right column says, “the difference of the morning  and afternoon temperatures.” In the third row, the left column says, “Step 3. Write a phrase that gives the information to find it.” Next to this in the right column, it says “the difference of 11 and negative 9.” In the fourth row, the left column says, “Step 4. Translate the phrase to an expression.” The right column contains 11 minus negative 9. In the fifth row, the left column says, “Step 5. Simplify the expression.” The right column contains 20. The final row says, “Step five. Write a complete sentence that answers the question.” Next to this in the right column, it says “the difference in temperatures was 20 degrees.”
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Source:  OpenStax, Elementary algebra. OpenStax CNX. Jan 18, 2017 Download for free at http://cnx.org/content/col12116/1.2
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