Question

Simplify 3 ( x + 2 ) − 2 ( x 2 + 2x − 4 ).

Which of the polynomials below represents the answer written in standard form?

Select one:
a. - 2x 2 − x + 14
b. - 2 + 7x + 2x 2
c. - 3x 4 + 14
d. 2x 2 + 7x − 2

Answer 1

The polynomials that represents the answer is -2x² - x + 14 ⇒ a

Explanation:

Let us solve the question

∵ The expression is 3(x + 2) - 2(x² + 2x - 4)

→ Multiply each bracket by the number before it

∵ 3(x + 2) = 3(x) + 3(2)

∴ 3(x - 2) = 3x + 6

∵ 2(x² + 2x - 4) = 2(x²) + 2(2x) + 2(-4)

∴ 2(x² + 2x - 4) = 2x² + 4x + (-8)

→ Remember (+)(-) = (-)

∴ 2(x² + 2x - 4) = 2x² + 4x - 8

∴ 3(x + 2) - 2(x² + 2x - 4) = (3x + 6) - (2x² + 4x - 8)

→ Multiply the (-) by all the terms in the 2nd bracket

∴ 3(x + 2) - 2(x² + 2x - 4) = 3x + 6 - 2x² - 4x + 8

→ Add the like terms

∵ 3(x + 2) - 2(x² + 2x - 4) = -2x² + (3x - 4x) + (6 + 8)

∴ 3(x + 2) - 2(x² + 2x - 4) = -2x² + (-x) + 14

∴ 3(x + 2) - 2(x² + 2x - 4) = -2x² - x + 14

∴ The polynomials that represents the answer is -2x² - x + 14