F(a)=8a^2+26a-7

Solution for F(a)=8a^2+26a-7 equation:

(F)=8F^2+26F-7

We move all terms to the left:

(F)-(8F^2+26F-7)=0

We get rid of parentheses

-8F^2+F-26F+7=0

We add all the numbers together, and all the variables

-8F^2-25F+7=0

a = -8; b = -25; c = +7;
Δ = b2-4ac
Δ = -252-4·(-8)·7
Δ = 849
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{-(-25)-\sqrt{849}}{2*-8}=\frac{25-\sqrt{849}}{-16}
$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-25)+\sqrt{849}}{2*-8}=\frac{25+\sqrt{849}}{-16}
$