X2-9.0x=15.75

Solution for X2-9.0x=15.75 equation:

X2-9.0X=15.75

We move all terms to the left:

X2-9.0X-(15.75)=0

We add all the numbers together, and all the variables

X^2-9X-15.75=0

a = 1; b = -9; c = -15.75;
Δ = b2-4ac
Δ = -92-4·1·(-15.75)
Δ = 144
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{144}=12$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-9)-12}{2*1}=\frac{-3}{2}
=-1+1/2
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-9)+12}{2*1}=\frac{21}{2}
=10+1/2
$