Question

question
factor the trinomial:
$5x^2 + 21x + 18$

Explanation:

Step1: Split middle term

Find two numbers that multiply to $5\times18=90$ and add to 21: 15 and 6.
$5x^2 + 15x + 6x + 18$

Step2: Group terms and factor

Group first/second and third/fourth terms.
$(5x^2 + 15x) + (6x + 18)$
Factor out GCF from each group:
$5x(x + 3) + 6(x + 3)$

Step3: Factor out common binomial

Extract $(x+3)$ from both terms.
$(5x + 6)(x + 3)$

Answer:

$(5x + 6)(x + 3)$