a(a+3)=2a+6

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

a(a+3)=2a+6

We move all terms to the left:

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

We multiply parentheses

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

We get rid of parentheses

a^2+3a-2a-6=0

We add all the numbers together, and all the variables

a^2+a-6=0

a = 1; b = 1; c = -6;
Δ = b2-4ac
Δ = 12-4·1·(-6)
Δ = 25
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{25}=5$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(1)-5}{2*1}=\frac{-6}{2}
=-3
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1)+5}{2*1}=\frac{4}{2}
=2
$