7x2-15x-25=0

Solution for 7x2-15x-25=0 equation:

7x^2-15x-25=0

a = 7; b = -15; c = -25;
Δ = b2-4ac
Δ = -152-4·7·(-25)
Δ = 925
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:

$\sqrt{\Delta}=\sqrt{925}=\sqrt{25*37}=\sqrt{25}*\sqrt{37}=5\sqrt{37}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-15)-5\sqrt{37}}{2*7}=\frac{15-5\sqrt{37}}{14}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-15)+5\sqrt{37}}{2*7}=\frac{15+5\sqrt{37}}{14}
$