F(x)=(330+15x)(6-0.25x)

Solution for F(x)=(330+15x)(6-0.25x) equation:

(F)=(330+15F)(6-0.25F)

We move all terms to the left:

(F)-((330+15F)(6-0.25F))=0

We add all the numbers together, and all the variables

F-((15F+330)(-0.25F+6))=0

We multiply parentheses ..

-((+0F^2+90F+0F+1980))+F=0


We calculate terms in parentheses: -((+0F^2+90F+0F+1980)), so:

(+0F^2+90F+0F+1980)

We get rid of parentheses

0F^2+90F+0F+1980

We add all the numbers together, and all the variables

F^2+91F+1980

Back to the equation:

-(F^2+91F+1980)


We add all the numbers together, and all the variables

F-(F^2+91F+1980)=0

We get rid of parentheses

-F^2+F-91F-1980=0

We add all the numbers together, and all the variables

-1F^2-90F-1980=0

a = -1; b = -90; c = -1980;
Δ = b2-4ac
Δ = -902-4·(-1)·(-1980)
Δ = 180
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:

$\sqrt{\Delta}=\sqrt{180}=\sqrt{36*5}=\sqrt{36}*\sqrt{5}=6\sqrt{5}$
$F_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-90)-6\sqrt{5}}{2*-1}=\frac{90-6\sqrt{5}}{-2}
$
$F_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-90)+6\sqrt{5}}{2*-1}=\frac{90+6\sqrt{5}}{-2}
$