F(-4)=2x^2-10x

Solution for F(-4)=2x^2-10x equation:

(-4)=2F^2-10F

We move all terms to the left:

(-4)-(2F^2-10F)=0

We add all the numbers together, and all the variables

-(2F^2-10F)-4=0

We get rid of parentheses

-2F^2+10F-4=0

a = -2; b = 10; c = -4;
Δ = b2-4ac
Δ = 102-4·(-2)·(-4)
Δ = 68
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$F_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{68}=\sqrt{4*17}=\sqrt{4}*\sqrt{17}=2\sqrt{17}$
$F_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(10)-2\sqrt{17}}{2*-2}=\frac{-10-2\sqrt{17}}{-4}
$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(10)+2\sqrt{17}}{2*-2}=\frac{-10+2\sqrt{17}}{-4}
$