x2+3x=67.5

Solution for x2+3x=67.5 equation:

x2+3x=67.5

We move all terms to the left:

x2+3x-(67.5)=0

We add all the numbers together, and all the variables

x^2+3x-67.5=0

a = 1; b = 3; c = -67.5;
Δ = b2-4ac
Δ = 32-4·1·(-67.5)
Δ = 279
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:

$\sqrt{\Delta}=\sqrt{279}=\sqrt{9*31}=\sqrt{9}*\sqrt{31}=3\sqrt{31}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(3)-3\sqrt{31}}{2*1}=\frac{-3-3\sqrt{31}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(3)+3\sqrt{31}}{2*1}=\frac{-3+3\sqrt{31}}{2}
$