C=0.3x^2-10x+7

Solution for C=0.3x^2-10x+7 equation:

=0.3C^2-10C+7

We move all terms to the left:

-(0.3C^2-10C+7)=0

We get rid of parentheses

-0.3C^2+10C-7=0

a = -0.3; b = 10; c = -7;
Δ = b2-4ac
Δ = 102-4·(-0.3)·(-7)
Δ = 91.6
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$C_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$C_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$C_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(10)-\sqrt{91.6}}{2*-0.3}=\frac{-10-\sqrt{91.6}}{-0.6}
$
$C_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(10)+\sqrt{91.6}}{2*-0.3}=\frac{-10+\sqrt{91.6}}{-0.6}
$