2(3x^2+4x-15)=0

Solution for 2(3x^2+4x-15)=0 equation:

2(3x^2+4x-15)=0

We multiply parentheses

6x^2+8x-30=0

a = 6; b = 8; c = -30;
Δ = b2-4ac
Δ = 82-4·6·(-30)
Δ = 784
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{784}=28$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(8)-28}{2*6}=\frac{-36}{12}
=-3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(8)+28}{2*6}=\frac{20}{12}
=1+2/3
$