5x(4x+5)=625

Solution for 5x(4x+5)=625 equation:

5x(4x+5)=625

We move all terms to the left:

5x(4x+5)-(625)=0

We multiply parentheses

20x^2+25x-625=0

a = 20; b = 25; c = -625;
Δ = b2-4ac
Δ = 252-4·20·(-625)
Δ = 50625
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{50625}=225$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(25)-225}{2*20}=\frac{-250}{40}
=-6+1/4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(25)+225}{2*20}=\frac{200}{40}
=5
$