8x^2+16x=90

Solution for 8x^2+16x=90 equation:

8x^2+16x=90

We move all terms to the left:

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