F(x)=-25^4+9x^2

Solution for F(x)=-25^4+9x^2 equation:

(F)=-25^4+9F^2

We move all terms to the left:

(F)-(-25^4+9F^2)=0

We get rid of parentheses

-9F^2+F+25^4=0

We add all the numbers together, and all the variables

-9F^2+F+390625=0

a = -9; b = 1; c = +390625;
Δ = b2-4ac
Δ = 12-4·(-9)·390625
Δ = 14062501
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$F_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$F_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(1)-\sqrt{14062501}}{2*-9}=\frac{-1-\sqrt{14062501}}{-18}
$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1)+\sqrt{14062501}}{2*-9}=\frac{-1+\sqrt{14062501}}{-18}
$