15=4x(x-1)

Solution for 15=4x(x-1) equation:

15=4x(x-1)

We move all terms to the left:

15-(4x(x-1))=0


We calculate terms in parentheses: -(4x(x-1)), so:

4x(x-1)

We multiply parentheses

4x^2-4x

Back to the equation:

-(4x^2-4x)


We get rid of parentheses

-4x^2+4x+15=0

a = -4; b = 4; c = +15;
Δ = b2-4ac
Δ = 42-4·(-4)·15
Δ = 256
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{256}=16$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(4)-16}{2*-4}=\frac{-20}{-8}
=2+1/2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(4)+16}{2*-4}=\frac{12}{-8}
=-1+1/2
$