How do you combine (x^2-bx-7) - (3x^2+2x-4)(x2bx7)(3x2+2x4)?

2 Answers
Jul 22, 2015

Group by like powers of xx and perform standard arithmetic to get:
color(white)("XXXX")XXXX-2x^2-(b+2)x -32x2(b+2)x3

Explanation:

(x^2−bx−7)−(3x^2+2x−4)(x2bx7)(3x2+2x4)
color(white)("XXXX")XXXXRegroup as:
(x^2-3x^2) + (-bx -2x) + (-7 -(-4))(x23x2)+(bx2x)+(7(4))

=-2x^2 -(b+2)x -3=2x2(b+2)x3

Jul 22, 2015

(x^2-bx-7)-(3x^2+2x-4)=-2x^2-bx-2x-3(x2bx7)(3x2+2x4)=2x2bx2x3

Explanation:

(x^2-bx-7)-(3x^2+2x-4)(x2bx7)(3x2+2x4)

Distribute the negative sign to each of the terms inside the second set of parentheses, then remove the parentheses.

x^2-bx-7-3x^2-2x+4x2bx73x22x+4

Group like terms.

x^2-3x^2-bx-2x-7+4x23x2bx2x7+4

Combine.

-2x^2-bx-2x-32x2bx2x3