How do you solve $(x - 4)(x + 5) = 7$ using the quadratic formula?

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Answer 1 · 2016-02-20T08:20:14

$x=(-1 +-sqrt109)/2$

Simplify the equation by FOIL METHOD
$(x-4)(x+5)=7$
$x^2+5x-4x-20=7$
#x^2+x-27=0
Identify the values for a, b, and c
$a=1$
$b=1$
$c=-27$
Use the standard formula, which is
$x=(-b+-sqrt(b^2-4ac))/(2a)$
Plug in the values
$x=(-1+-sqrt(1^2-4(1)(-27)))/(2(1))$
$x=(-1+-sqrt(1+108))/2$
$x=(-1+-sqrt109)/2$
Answer
$x=(-1+-sqrt109)/2$

How do you solve (x - 4)(x + 5) = 7(x - 4)(x + 5) = 7 using the quadratic formula?