8x^2-16x-90=0

Solution for 8x^2-16x-90=0 equation:

8x^2-16x-90=0

a = 8; b = -16; c = -90;
Δ = b2-4ac
Δ = -162-4·8·(-90)
Δ = 3136
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{3136}=56$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-16)-56}{2*8}=\frac{-40}{16}
=-2+1/2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-16)+56}{2*8}=\frac{72}{16}
=4+1/2
$