-4x(3-x)=12

Solution for -4x(3-x)=12 equation:

-4x(3-x)=12

We move all terms to the left:

-4x(3-x)-(12)=0

We add all the numbers together, and all the variables

-4x(-1x+3)-12=0

We multiply parentheses

4x^2-12x-12=0

a = 4; b = -12; c = -12;
Δ = b2-4ac
Δ = -122-4·4·(-12)
Δ = 336
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:

$\sqrt{\Delta}=\sqrt{336}=\sqrt{16*21}=\sqrt{16}*\sqrt{21}=4\sqrt{21}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-12)-4\sqrt{21}}{2*4}=\frac{12-4\sqrt{21}}{8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-12)+4\sqrt{21}}{2*4}=\frac{12+4\sqrt{21}}{8}
$