20=-2x^2+14x

Solution for 20=-2x^2+14x equation:

20=-2x^2+14x

We move all terms to the left:

20-(-2x^2+14x)=0

We get rid of parentheses

2x^2-14x+20=0

a = 2; b = -14; c = +20;
Δ = b2-4ac
Δ = -142-4·2·20
Δ = 36
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{36}=6$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-14)-6}{2*2}=\frac{8}{4}
=2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-14)+6}{2*2}=\frac{20}{4}
=5
$