144=x^2+3x

Solution for 144=x^2+3x equation:

144=x^2+3x

We move all terms to the left:

144-(x^2+3x)=0

We get rid of parentheses

-x^2-3x+144=0

We add all the numbers together, and all the variables

-1x^2-3x+144=0

a = -1; b = -3; c = +144;
Δ = b2-4ac
Δ = -32-4·(-1)·144
Δ = 585
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:

$\sqrt{\Delta}=\sqrt{585}=\sqrt{9*65}=\sqrt{9}*\sqrt{65}=3\sqrt{65}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-3)-3\sqrt{65}}{2*-1}=\frac{3-3\sqrt{65}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-3)+3\sqrt{65}}{2*-1}=\frac{3+3\sqrt{65}}{-2}
$