Question

factor trinomials (a>1) level 3
score: 13.75/20 penalty: 0.25 off
question
factor completely.
$5x^2 + 21x + 4$

Explanation:

Step1: Find product of a and c

$a=5, c=4$, so $5×4=20$

Step2: Find two numbers for sum 21

Numbers: 20 and 1 (20+1=21)

Step3: Split middle term

$5x^2 + 20x + x + 4$

Step4: Factor by grouping

$5x(x + 4) + 1(x + 4)$

Step5: Factor out common binomial

$(5x + 1)(x + 4)$

Answer:

$(5x + 1)(x + 4)$