C=7y(5+9y)

Solution for C=7y(5+9y) equation:

=7C(5+9C)

We move all terms to the left:

-(7C(5+9C))=0

We add all the numbers together, and all the variables

-(7C(9C+5))=0


We calculate terms in parentheses: -(7C(9C+5)), so:

7C(9C+5)

We multiply parentheses

63C^2+35C

Back to the equation:

-(63C^2+35C)


We get rid of parentheses

-63C^2-35C=0

a = -63; b = -35; c = 0;
Δ = b2-4ac
Δ = -352-4·(-63)·0
Δ = 1225
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$C_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$C_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1225}=35$
$C_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-35)-35}{2*-63}=\frac{0}{-126}
=0
$
$C_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-35)+35}{2*-63}=\frac{70}{-126}
=-5/9
$