Question

Simplify the expression (4x − 3)(x + 5). 4x2 − 17x + 15 4x2 − 17x − 15 4x2 + 17x + 15 4x2 + 17x − 15

Answer 1

A) $(4x-3)(x+5)=$

$*(a+b)(c+d)=ac+ad+bc+bd$

$Soo..$

$4x*x+4x*5-3*x-3*5=$

$=4 x^{2} +20x-3x-15$

$=4x^{2} +17x-15$

b) $4x^{2} -17x+15=$

$=(4x-5)(x-3)$

c) $4 x^{2} -17x-15=$

$=(4x+3)(x-5)$

d) $4 x^{2} +17x+15=$
$=(4x+5)(x+3)$


e)$4 x^{2} +17x-15=$
$=(4x-3)(x+5)$

Answer 2

There are mnemonic acronyms out there for reminding you how to do this. I think of it simply as using the distributive property.
  (4x-3)(x+5) = 4x(x+5) -3(x+5)
then again
  = (4x² +20x) + (-3x -15)
  = 4x² + (20-3)x -15 . . . . . . . combine like terms
  = 4x² +17x -15