x^2+2x=7.2

Solution for x^2+2x=7.2 equation:

x^2+2x=7.2

We move all terms to the left:

x^2+2x-(7.2)=0

We add all the numbers together, and all the variables

x^2+2x-7.2=0

a = 1; b = 2; c = -7.2;
Δ = b2-4ac
Δ = 22-4·1·(-7.2)
Δ = 32.8
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(2)-\sqrt{32.8}}{2*1}=\frac{-2-\sqrt{32.8}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(2)+\sqrt{32.8}}{2*1}=\frac{-2+\sqrt{32.8}}{2}
$