11)
Find two numbers that multiply together to equal 9 * 10 = 90, and add together to equal 21.
9 and 10 do not add to 21.
15*6 = 90
15 + 6 = 21
Since 15 and 6 make both true, then split 21x into 15x and 6x.
9x² + 6x + 15x + 10
Factor a 3x out of the first two terms and factor a 5 out of the last two terms.
3x(3x + 2) + 5(3x+2)
Factor our (3x+2) out of both, leaving you with (3x+5)
9x²+21x+10 = (3x+5)(3x+2)
