-8x^2+55x+72=0

Solution for -8x^2+55x+72=0 equation:

-8x^2+55x+72=0

a = -8; b = 55; c = +72;
Δ = b2-4ac
Δ = 552-4·(-8)·72
Δ = 5329
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{5329}=73$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(55)-73}{2*-8}=\frac{-128}{-16}
=+8
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(55)+73}{2*-8}=\frac{18}{-16}
=-1+1/8
$