Question

Determine the factors of 3x2 + 10x − 8. (Which is the right answer?)

A. (3x − 8)(x + 1)
B. (3x − 1)(x + 8)
C. (3x − 4)(x + 2)
D. (3x − 2)(x + 4)

Answer 1

ANSWER

$(3x - 2)(x + 4)$

EXPLANATION

The given quadratic trinomial is

$3 {x}^{2} + 10x - 8$

Comparing to the general quadratic trinomial:

$a{x}^{2} + bx + c$

We have a=1, b=10 and c=-8

$ac = 3 \times - 8 = - 24$

The factors of -24 that adds up to 10 are -2 and 12.

We split the middle term to obtain;

$3 {x}^{2} + 12x - 2x- 8$

Factor;

$3x(x+ 4) - 2(x + 4)$

Factor further;

$(3x - 2)(x + 4)$

The last option is correct.