(2a-6)(a+3)=260

Solution for (2a-6)(a+3)=260 equation:

(2a-6)(a+3)=260

We move all terms to the left:

(2a-6)(a+3)-(260)=0

We multiply parentheses ..

(+2a^2+6a-6a-18)-260=0

We get rid of parentheses

2a^2+6a-6a-18-260=0

We add all the numbers together, and all the variables

2a^2-278=0

a = 2; b = 0; c = -278;
Δ = b2-4ac
Δ = 02-4·2·(-278)
Δ = 2224
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{2224}=\sqrt{16*139}=\sqrt{16}*\sqrt{139}=4\sqrt{139}$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-4\sqrt{139}}{2*2}=\frac{0-4\sqrt{139}}{4}
=-\frac{4\sqrt{139}}{4}
=-\sqrt{139}
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+4\sqrt{139}}{2*2}=\frac{0+4\sqrt{139}}{4}
=\frac{4\sqrt{139}}{4}
=\sqrt{139}
$