2y^2-12y-15=0

Solution for 2y^2-12y-15=0 equation:

2y^2-12y-15=0

a = 2; b = -12; c = -15;
Δ = b2-4ac
Δ = -122-4·2·(-15)
Δ = 264
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:

$\sqrt{\Delta}=\sqrt{264}=\sqrt{4*66}=\sqrt{4}*\sqrt{66}=2\sqrt{66}$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-12)-2\sqrt{66}}{2*2}=\frac{12-2\sqrt{66}}{4}
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-12)+2\sqrt{66}}{2*2}=\frac{12+2\sqrt{66}}{4}
$