7x(x+15)=279

Solution for 7x(x+15)=279 equation:

7x(x+15)=279

We move all terms to the left:

7x(x+15)-(279)=0

We multiply parentheses

7x^2+105x-279=0

a = 7; b = 105; c = -279;
Δ = b2-4ac
Δ = 1052-4·7·(-279)
Δ = 18837
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:

$\sqrt{\Delta}=\sqrt{18837}=\sqrt{9*2093}=\sqrt{9}*\sqrt{2093}=3\sqrt{2093}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(105)-3\sqrt{2093}}{2*7}=\frac{-105-3\sqrt{2093}}{14}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(105)+3\sqrt{2093}}{2*7}=\frac{-105+3\sqrt{2093}}{14}
$