20=-16x^2+48x+36

Solution for 20=-16x^2+48x+36 equation:

20=-16x^2+48x+36

We move all terms to the left:

20-(-16x^2+48x+36)=0

We get rid of parentheses

16x^2-48x-36+20=0

We add all the numbers together, and all the variables

16x^2-48x-16=0

a = 16; b = -48; c = -16;
Δ = b2-4ac
Δ = -482-4·16·(-16)
Δ = 3328
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:

$\sqrt{\Delta}=\sqrt{3328}=\sqrt{256*13}=\sqrt{256}*\sqrt{13}=16\sqrt{13}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-48)-16\sqrt{13}}{2*16}=\frac{48-16\sqrt{13}}{32}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-48)+16\sqrt{13}}{2*16}=\frac{48+16\sqrt{13}}{32}
$