7x^2-2x-20=0

Solution for 7x^2-2x-20=0 equation:

7x^2-2x-20=0

a = 7; b = -2; c = -20;
Δ = b2-4ac
Δ = -22-4·7·(-20)
Δ = 564
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:

$\sqrt{\Delta}=\sqrt{564}=\sqrt{4*141}=\sqrt{4}*\sqrt{141}=2\sqrt{141}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-2)-2\sqrt{141}}{2*7}=\frac{2-2\sqrt{141}}{14}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-2)+2\sqrt{141}}{2*7}=\frac{2+2\sqrt{141}}{14}
$