F(0)=x^2-7x-9

Solution for F(0)=x^2-7x-9 equation:

(0)=F^2-7F-9

We move all terms to the left:

(0)-(F^2-7F-9)=0

We add all the numbers together, and all the variables

-(F^2-7F-9)=0

We get rid of parentheses

-F^2+7F+9=0

We add all the numbers together, and all the variables

-1F^2+7F+9=0

a = -1; b = 7; c = +9;
Δ = b2-4ac
Δ = 72-4·(-1)·9
Δ = 85
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{-(7)-\sqrt{85}}{2*-1}=\frac{-7-\sqrt{85}}{-2}
$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(7)+\sqrt{85}}{2*-1}=\frac{-7+\sqrt{85}}{-2}
$