F(x)=3x^2+30x+21

Solution for F(x)=3x^2+30x+21 equation:

(F)=3F^2+30F+21

We move all terms to the left:

(F)-(3F^2+30F+21)=0

We get rid of parentheses

-3F^2+F-30F-21=0

We add all the numbers together, and all the variables

-3F^2-29F-21=0

a = -3; b = -29; c = -21;
Δ = b2-4ac
Δ = -292-4·(-3)·(-21)
Δ = 589
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{-(-29)-\sqrt{589}}{2*-3}=\frac{29-\sqrt{589}}{-6}
$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-29)+\sqrt{589}}{2*-3}=\frac{29+\sqrt{589}}{-6}
$