9. Which one of the following pairs of integers has a product of –15 and a sum of –2?

Question

asked Nov 3, 2022 8.2k views

1 Answer

Sumit Chauhan · Answer 1 · 2022-11-09T19:24:03+0000

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Begin by creating the two equations that are provided by the information in the question.

x+y=8

and

xy = -15

Now you can solve logically because of the simplicity of the numbers, by listing the factors of 15 and determine which pair will add up to 8

1 and -15

3 and- 5

The Answer is 3 and 5

Or you can solve algebraically by substitution

x+y=8

can be converted to

y=8−x

Now substitute the first equation into the second equation for the y variable.

x(8−x)= 15

8x−x^2=15

Set the equation equal to zero.

8x−x^2−15=15−15

−x^2+8x−15=0

Factor the trinomial.

-1(x+5)(x-3) = 0#

Set both factors equal to zero.

x+5=0

x=-5

x−3=0

x=3