20(x)=20-13x^2

Solution for 20(x)=20-13x^2 equation:

20(x)=20-13x^2

We move all terms to the left:

20(x)-(20-13x^2)=0

We get rid of parentheses

13x^2+20x-20=0

a = 13; b = 20; c = -20;
Δ = b2-4ac
Δ = 202-4·13·(-20)
Δ = 1440
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:

$\sqrt{\Delta}=\sqrt{1440}=\sqrt{144*10}=\sqrt{144}*\sqrt{10}=12\sqrt{10}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(20)-12\sqrt{10}}{2*13}=\frac{-20-12\sqrt{10}}{26}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+12\sqrt{10}}{2*13}=\frac{-20+12\sqrt{10}}{26}
$