-21x^2-132x+115=0

Solution for -21x^2-132x+115=0 equation:

-21x^2-132x+115=0

a = -21; b = -132; c = +115;
Δ = b2-4ac
Δ = -1322-4·(-21)·115
Δ = 27084
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{27084}=\sqrt{4*6771}=\sqrt{4}*\sqrt{6771}=2\sqrt{6771}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-132)-2\sqrt{6771}}{2*-21}=\frac{132-2\sqrt{6771}}{-42}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-132)+2\sqrt{6771}}{2*-21}=\frac{132+2\sqrt{6771}}{-42}
$