x^2-3.5=8.75

Solution for x^2-3.5=8.75 equation:

x^2-3.5=8.75

We move all terms to the left:

x^2-3.5-(8.75)=0

We add all the numbers together, and all the variables

x^2-12.25=0

a = 1; b = 0; c = -12.25;
Δ = b2-4ac
Δ = 02-4·1·(-12.25)
Δ = 49
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{49}=7$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-7}{2*1}=\frac{-7}{2}
=-3+1/2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+7}{2*1}=\frac{7}{2}
=3+1/2
$