7x^2+28x-5=0

Solution for 7x^2+28x-5=0 equation:

7x^2+28x-5=0

a = 7; b = 28; c = -5;
Δ = b2-4ac
Δ = 282-4·7·(-5)
Δ = 924
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:

$\sqrt{\Delta}=\sqrt{924}=\sqrt{4*231}=\sqrt{4}*\sqrt{231}=2\sqrt{231}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(28)-2\sqrt{231}}{2*7}=\frac{-28-2\sqrt{231}}{14}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(28)+2\sqrt{231}}{2*7}=\frac{-28+2\sqrt{231}}{14}
$