2a(a+7)=36

Solution for 2a(a+7)=36 equation:

2a(a+7)=36

We move all terms to the left:

2a(a+7)-(36)=0

We multiply parentheses

2a^2+14a-36=0

a = 2; b = 14; c = -36;
Δ = b2-4ac
Δ = 142-4·2·(-36)
Δ = 484
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{484}=22$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(14)-22}{2*2}=\frac{-36}{4}
=-9
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(14)+22}{2*2}=\frac{8}{4}
=2
$