Question

What algebraic expression must be added to the sum of 3x2 +4x+8 and 2x2−6x+3 to give 9x2−2x−5 as the result?

Answer 1

`4x^2-16`

Explanation:

-This is an addition/subtraction problem.

#We subtract the sum of the first two expression from the third expression:

`\#Add \ first \ two\\\\=3x^2 +4x+8 +2x^2-6x+3\\\\=5x^2-2x+11\\\\\# Subtract\ from \ the \ third\\=(9x^2-2x-5)-(5x^2-2x+11)\\\\=9x^2-2x-5-5x^2+2x-11\\\\=4x^2-16`

Hence, the expression
`4x^2-16` must be added to the first two.