2z^2-5z+4=0

Solution for 2z^2-5z+4=0 equation:

Simplifying
2z2 + -5z + 4 = 0

Reorder the terms:
4 + -5z + 2z2 = 0

Solving
4 + -5z + 2z2 = 0

Solving for variable 'z'.

Begin completing the square.  Divide all terms by
2 the coefficient of the squared term: 

Divide each side by '2'.
2 + -2.5z + z2 = 0

Move the constant term to the right:

Add '-2' to each side of the equation.
2 + -2.5z + -2 + z2 = 0 + -2

Reorder the terms:
2 + -2 + -2.5z + z2 = 0 + -2

Combine like terms: 2 + -2 = 0
0 + -2.5z + z2 = 0 + -2
-2.5z + z2 = 0 + -2

Combine like terms: 0 + -2 = -2
-2.5z + z2 = -2

The z term is -2.5z.  Take half its coefficient (-1.25).
Square it (1.5625) and add it to both sides.

Add '1.5625' to each side of the equation.
-2.5z + 1.5625 + z2 = -2 + 1.5625

Reorder the terms:
1.5625 + -2.5z + z2 = -2 + 1.5625

Combine like terms: -2 + 1.5625 = -0.4375
1.5625 + -2.5z + z2 = -0.4375

Factor a perfect square on the left side:
(z + -1.25)(z + -1.25) = -0.4375

Can't calculate square root of the right side.

The solution to this equation could not be determined.