The expression 10x^2-x-24 can be written as (Ax-8)(Bx+3), where A and B are integers. What is AB + B?

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1 Answer
Jun 7, 2018

AB+B=12, 65/8

Explanation:

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10x^2-x-24=(Ax-8)(Bx+3)

10x^2-x-24=ABx^2+3Ax-8Bx-24

10x^2-x-24=ABx^2-(8B-3A)x-24

AB=10

8B-3A=1, :. 8B=1+3A, B=(1+3A)/8

(A(1+3A))/8=10

3A^2+A-80=0

A=(-1+-sqrt(1-4(3)(-80)))/6=(-1+-sqrt961)/6=(-1+-31)/6

A=5, -16/3

A=5, :. B=2, :. AB+B=10+2=12

A=-16/3, :. B=-15/8, :. AB+B=10-15/8=65/8