5x(5x-3)=18

Solution for 5x(5x-3)=18 equation:

5x(5x-3)=18

We move all terms to the left:

5x(5x-3)-(18)=0

We multiply parentheses

25x^2-15x-18=0

a = 25; b = -15; c = -18;
Δ = b2-4ac
Δ = -152-4·25·(-18)
Δ = 2025
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2025}=45$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-15)-45}{2*25}=\frac{-30}{50}
=-3/5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-15)+45}{2*25}=\frac{60}{50}
=1+1/5
$