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Fine two integers that have a sum of -17 and a product of 52. What are the integers?

User Mkl Rjv
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1 Answer

3 votes

Answer:

{4, 13}

Explanation:

Represent the integers by I and J. Then I + J = -17 and I*J = 52.

Let's solve this system using substitution. Solve the first equation for I as follows:

I + J = -17 becomes I = -J - 17

Substitute -J -17 for I in the second equation:

(-J - 17)*J = 52

Performing the indicated multiplication, we get:

-J^2 - 17J - 52 = 0

Let's solve this using the quadratic formula. The quadratic coefficients here are {-1, -17, -52}, and so the discriminant, b^2 - 4ac, is

(-17)^2 - 4(-1)(-52), or 289 - 208, or 81. This result is positive, so we know that the quadratic equation has two real, unequal roots. They are:

17 ± √81 17 ± 9

J = --------------- = ---------------

2(-1) -2

Evaluating this last result, we get J = (17 + 9)/2, or J = 13, and

J = (17 - 9)/2 = 8/2, or J = 4

User Hawlett
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