7x^2+8x=15

Solution for 7x^2+8x=15 equation:

7x^2+8x=15

We move all terms to the left:

7x^2+8x-(15)=0

a = 7; b = 8; c = -15;
Δ = b2-4ac
Δ = 82-4·7·(-15)
Δ = 484
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{484}=22$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(8)-22}{2*7}=\frac{-30}{14}
=-2+1/7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(8)+22}{2*7}=\frac{14}{14}
=1
$