X^2-21.7x=-15.75

Solution for X^2-21.7x=-15.75 equation:

X^2-21.7X=-15.75

We move all terms to the left:

X^2-21.7X-(-15.75)=0

We add all the numbers together, and all the variables

X^2-21.7X+15.75=0

a = 1; b = -21.7; c = +15.75;
Δ = b2-4ac
Δ = -21.72-4·1·15.75
Δ = 407.89
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{-(-21.7)-\sqrt{407.89}}{2*1}=\frac{21.7-\sqrt{407.89}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-21.7)+\sqrt{407.89}}{2*1}=\frac{21.7+\sqrt{407.89}}{2}
$