1. (x - 8) (2x + 5) = 5
2. x² + 13x + 40 = 0
3. x² - 6x - 20 = 7
Part 1
apply distributive property left side
2x^2+5x-16x-40=5
2x^2-11x-45=0
Apply the formula to solve quadratic equation
we have
a=2
b=-11
c=-45
substitute
the solutions are
Part 2
x² + 13x + 40 = 0
we have
a=1
b=13
c=40
Apply the formula
so
x=-5 and x=-8
Part 3
x² - 6x - 20 = 7
x² - 6x - 27=0
so
a=1
b=-6
c=-27
Apply the formula
so
x=9 and x=-3