X(7x+8)=25

Solution for X(7x+8)=25 equation:

X(7X+8)=25

We move all terms to the left:

X(7X+8)-(25)=0

We multiply parentheses

7X^2+8X-25=0

a = 7; b = 8; c = -25;
Δ = b2-4ac
Δ = 82-4·7·(-25)
Δ = 764
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{764}=\sqrt{4*191}=\sqrt{4}*\sqrt{191}=2\sqrt{191}$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(8)-2\sqrt{191}}{2*7}=\frac{-8-2\sqrt{191}}{14}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(8)+2\sqrt{191}}{2*7}=\frac{-8+2\sqrt{191}}{14}
$