-9=-8y^2+6.2y

Solution for -9=-8y^2+6.2y equation:

-9=-8y^2+6.2y

We move all terms to the left:

-9-(-8y^2+6.2y)=0

We get rid of parentheses

8y^2-6.2y-9=0

a = 8; b = -6.2; c = -9;
Δ = b2-4ac
Δ = -6.22-4·8·(-9)
Δ = 326.44
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-6.2)-\sqrt{326.44}}{2*8}=\frac{6.2-\sqrt{326.44}}{16}
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-6.2)+\sqrt{326.44}}{2*8}=\frac{6.2+\sqrt{326.44}}{16}
$