7x^2-36x-18=0

Solution for 7x^2-36x-18=0 equation:

7x^2-36x-18=0

a = 7; b = -36; c = -18;
Δ = b2-4ac
Δ = -362-4·7·(-18)
Δ = 1800
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:

$\sqrt{\Delta}=\sqrt{1800}=\sqrt{900*2}=\sqrt{900}*\sqrt{2}=30\sqrt{2}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-36)-30\sqrt{2}}{2*7}=\frac{36-30\sqrt{2}}{14}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-36)+30\sqrt{2}}{2*7}=\frac{36+30\sqrt{2}}{14}
$