(y^2)-70y=800

Solution for (y^2)-70y=800 equation:

(y^2)-70y=800

We move all terms to the left:

(y^2)-70y-(800)=0

a = 1; b = -70; c = -800;
Δ = b2-4ac
Δ = -702-4·1·(-800)
Δ = 8100
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{8100}=90$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-70)-90}{2*1}=\frac{-20}{2}
=-10
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-70)+90}{2*1}=\frac{160}{2}
=80
$