z^2-5z+90=0

Solution for z^2-5z+90=0 equation:

Simplifying
z2 + -5z + 90 = 0

Reorder the terms:
90 + -5z + z2 = 0

Solving
90 + -5z + z2 = 0

Solving for variable 'z'.

Begin completing the square.

Move the constant term to the right:

Add '-90' to each side of the equation.
90 + -5z + -90 + z2 = 0 + -90

Reorder the terms:
90 + -90 + -5z + z2 = 0 + -90

Combine like terms: 90 + -90 = 0
0 + -5z + z2 = 0 + -90
-5z + z2 = 0 + -90

Combine like terms: 0 + -90 = -90
-5z + z2 = -90

The z term is -5z.  Take half its coefficient (-2.5).
Square it (6.25) and add it to both sides.

Add '6.25' to each side of the equation.
-5z + 6.25 + z2 = -90 + 6.25

Reorder the terms:
6.25 + -5z + z2 = -90 + 6.25

Combine like terms: -90 + 6.25 = -83.75
6.25 + -5z + z2 = -83.75

Factor a perfect square on the left side:
(z + -2.5)(z + -2.5) = -83.75

Can't calculate square root of the right side.

The solution to this equation could not be determined.