X^2-16x-57=-21

Solution for X^2-16x-57=-21 equation:

X^2-16X-57=-21

We move all terms to the left:

X^2-16X-57-(-21)=0

We add all the numbers together, and all the variables

X^2-16X-36=0

a = 1; b = -16; c = -36;
Δ = b2-4ac
Δ = -162-4·1·(-36)
Δ = 400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{400}=20$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-16)-20}{2*1}=\frac{-4}{2}
=-2
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-16)+20}{2*1}=\frac{36}{2}
=18
$