How do you factor $4x^2+15x+9$ ?

Question

11874 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2016-06-22T18:19:39

$4x^2+15x+9=(4x+3)(x+3)$

Use an AC method.

Find a pair of factors of $AC = 4*9 = 36$ with sum $B=15$

The pair $12, 3$ works in that $12+3 = 15$ and $12xx3=36$

Use this pair to split the middle term, then factor by grouping...

$4x^2+15x+9$

$=4x^2+12x+3x+9$

$=(4x^2+12x)+(3x+9)$

$=4x(x+3)+3(x+3)$

$=(4x+3)(x+3)$

How do you factor 4x^2+15x+94x^2+15x+9?