15x=1.25x^2

Solution for 15x=1.25x^2 equation:

15x=1.25x^2

We move all terms to the left:

15x-(1.25x^2)=0

We get rid of parentheses

-1.25x^2+15x=0

a = -1.25; b = 15; c = 0;
Δ = b2-4ac
Δ = 152-4·(-1.25)·0
Δ = 225
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{225}=15$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(15)-15}{2*-1.25}=\frac{-30}{-2.5}
=+12
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(15)+15}{2*-1.25}=\frac{0}{-2.5}
=0
$