-7y^2+91y-98=0

Solution for -7y^2+91y-98=0 equation:

-7y^2+91y-98=0

a = -7; b = 91; c = -98;
Δ = b2-4ac
Δ = 912-4·(-7)·(-98)
Δ = 5537
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{5537}=\sqrt{49*113}=\sqrt{49}*\sqrt{113}=7\sqrt{113}$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(91)-7\sqrt{113}}{2*-7}=\frac{-91-7\sqrt{113}}{-14}
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(91)+7\sqrt{113}}{2*-7}=\frac{-91+7\sqrt{113}}{-14}
$