128=-4(-5x+3)x=

Solution for 128=-4(-5x+3)x= equation:

128=-4(-5x+3)x=

We move all terms to the left:

128-(-4(-5x+3)x)=0


We calculate terms in parentheses: -(-4(-5x+3)x), so:

-4(-5x+3)x

We multiply parentheses

20x^2-12x

Back to the equation:

-(20x^2-12x)


We get rid of parentheses

-20x^2+12x+128=0

a = -20; b = 12; c = +128;
Δ = b2-4ac
Δ = 122-4·(-20)·128
Δ = 10384
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:

$\sqrt{\Delta}=\sqrt{10384}=\sqrt{16*649}=\sqrt{16}*\sqrt{649}=4\sqrt{649}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(12)-4\sqrt{649}}{2*-20}=\frac{-12-4\sqrt{649}}{-40}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(12)+4\sqrt{649}}{2*-20}=\frac{-12+4\sqrt{649}}{-40}
$