3x^2+4x-7=15

Solution for 3x^2+4x-7=15 equation:

3x^2+4x-7=15

We move all terms to the left:

3x^2+4x-7-(15)=0

We add all the numbers together, and all the variables

3x^2+4x-22=0

a = 3; b = 4; c = -22;
Δ = b2-4ac
Δ = 42-4·3·(-22)
Δ = 280
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:

$\sqrt{\Delta}=\sqrt{280}=\sqrt{4*70}=\sqrt{4}*\sqrt{70}=2\sqrt{70}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(4)-2\sqrt{70}}{2*3}=\frac{-4-2\sqrt{70}}{6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(4)+2\sqrt{70}}{2*3}=\frac{-4+2\sqrt{70}}{6}
$