z^2-18z-81=

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Solution for z^2-18z-81= equation:


Simplifying
z2 + -18z + -81 = 0

Reorder the terms:
-81 + -18z + z2 = 0

Solving
-81 + -18z + z2 = 0

Solving for variable 'z'.

Begin completing the square.

Move the constant term to the right:

Add '81' to each side of the equation.
-81 + -18z + 81 + z2 = 0 + 81

Reorder the terms:
-81 + 81 + -18z + z2 = 0 + 81

Combine like terms: -81 + 81 = 0
0 + -18z + z2 = 0 + 81
-18z + z2 = 0 + 81

Combine like terms: 0 + 81 = 81
-18z + z2 = 81

The z term is -18z.  Take half its coefficient (-9).
Square it (81) and add it to both sides.

Add '81' to each side of the equation.
-18z + 81 + z2 = 81 + 81

Reorder the terms:
81 + -18z + z2 = 81 + 81

Combine like terms: 81 + 81 = 162
81 + -18z + z2 = 162

Factor a perfect square on the left side:
(z + -9)(z + -9) = 162

Calculate the square root of the right side: 12.727922061

Break this problem into two subproblems by setting 
(z + -9) equal to 12.727922061 and -12.727922061.

Subproblem 1

z + -9 = 12.727922061 Simplifying z + -9 = 12.727922061 Reorder the terms: -9 + z = 12.727922061 Solving -9 + z = 12.727922061 Solving for variable 'z'. Move all terms containing z to the left, all other terms to the right. Add '9' to each side of the equation. -9 + 9 + z = 12.727922061 + 9 Combine like terms: -9 + 9 = 0 0 + z = 12.727922061 + 9 z = 12.727922061 + 9 Combine like terms: 12.727922061 + 9 = 21.727922061 z = 21.727922061 Simplifying z = 21.727922061

Subproblem 2

z + -9 = -12.727922061 Simplifying z + -9 = -12.727922061 Reorder the terms: -9 + z = -12.727922061 Solving -9 + z = -12.727922061 Solving for variable 'z'. Move all terms containing z to the left, all other terms to the right. Add '9' to each side of the equation. -9 + 9 + z = -12.727922061 + 9 Combine like terms: -9 + 9 = 0 0 + z = -12.727922061 + 9 z = -12.727922061 + 9 Combine like terms: -12.727922061 + 9 = -3.727922061 z = -3.727922061 Simplifying z = -3.727922061

Solution

The solution to the problem is based on the solutions from the subproblems. z = {21.727922061, -3.727922061}

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