Answer:
(k + 7)(3k - 8)
Step-by-step explanation:
To factor the quadratic
Consider the factors of the product of the k² term and the constant term which sum to give the coefficient of the k- term
product = 3 × - 56 = - 168 and sum = + 13
The factors are + 21 and - 8
Use these factors to split the k- term
3k² + 21k - 8k - 56 ( factor the first/second and third/fourth terms )
= 3k(k + 7) - 8(k + 7) ← factor out (k + 7)
= (k + 7)(3k - 8)
