4z^2-20z+15=0

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Solution for 4z^2-20z+15=0 equation:


Simplifying
4z2 + -20z + 15 = 0

Reorder the terms:
15 + -20z + 4z2 = 0

Solving
15 + -20z + 4z2 = 0

Solving for variable 'z'.

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

Divide each side by '4'.
3.75 + -5z + z2 = 0

Move the constant term to the right:

Add '-3.75' to each side of the equation.
3.75 + -5z + -3.75 + z2 = 0 + -3.75

Reorder the terms:
3.75 + -3.75 + -5z + z2 = 0 + -3.75

Combine like terms: 3.75 + -3.75 = 0.00
0.00 + -5z + z2 = 0 + -3.75
-5z + z2 = 0 + -3.75

Combine like terms: 0 + -3.75 = -3.75
-5z + z2 = -3.75

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 = -3.75 + 6.25

Reorder the terms:
6.25 + -5z + z2 = -3.75 + 6.25

Combine like terms: -3.75 + 6.25 = 2.5
6.25 + -5z + z2 = 2.5

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

Calculate the square root of the right side: 1.58113883

Break this problem into two subproblems by setting 
(z + -2.5) equal to 1.58113883 and -1.58113883.

Subproblem 1

z + -2.5 = 1.58113883 Simplifying z + -2.5 = 1.58113883 Reorder the terms: -2.5 + z = 1.58113883 Solving -2.5 + z = 1.58113883 Solving for variable 'z'. Move all terms containing z to the left, all other terms to the right. Add '2.5' to each side of the equation. -2.5 + 2.5 + z = 1.58113883 + 2.5 Combine like terms: -2.5 + 2.5 = 0.0 0.0 + z = 1.58113883 + 2.5 z = 1.58113883 + 2.5 Combine like terms: 1.58113883 + 2.5 = 4.08113883 z = 4.08113883 Simplifying z = 4.08113883

Subproblem 2

z + -2.5 = -1.58113883 Simplifying z + -2.5 = -1.58113883 Reorder the terms: -2.5 + z = -1.58113883 Solving -2.5 + z = -1.58113883 Solving for variable 'z'. Move all terms containing z to the left, all other terms to the right. Add '2.5' to each side of the equation. -2.5 + 2.5 + z = -1.58113883 + 2.5 Combine like terms: -2.5 + 2.5 = 0.0 0.0 + z = -1.58113883 + 2.5 z = -1.58113883 + 2.5 Combine like terms: -1.58113883 + 2.5 = 0.91886117 z = 0.91886117 Simplifying z = 0.91886117

Solution

The solution to the problem is based on the solutions from the subproblems. z = {4.08113883, 0.91886117}

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