-x^2+18x+81=25

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Solution for -x^2+18x+81=25 equation:


Simplifying
-1x2 + 18x + 81 = 25

Reorder the terms:
81 + 18x + -1x2 = 25

Solving
81 + 18x + -1x2 = 25

Solving for variable 'x'.

Reorder the terms:
81 + -25 + 18x + -1x2 = 25 + -25

Combine like terms: 81 + -25 = 56
56 + 18x + -1x2 = 25 + -25

Combine like terms: 25 + -25 = 0
56 + 18x + -1x2 = 0

Begin completing the square.  Divide all terms by
-1 the coefficient of the squared term: 

Divide each side by '-1'.
-56 + -18x + x2 = 0

Move the constant term to the right:

Add '56' to each side of the equation.
-56 + -18x + 56 + x2 = 0 + 56

Reorder the terms:
-56 + 56 + -18x + x2 = 0 + 56

Combine like terms: -56 + 56 = 0
0 + -18x + x2 = 0 + 56
-18x + x2 = 0 + 56

Combine like terms: 0 + 56 = 56
-18x + x2 = 56

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

Add '81' to each side of the equation.
-18x + 81 + x2 = 56 + 81

Reorder the terms:
81 + -18x + x2 = 56 + 81

Combine like terms: 56 + 81 = 137
81 + -18x + x2 = 137

Factor a perfect square on the left side:
(x + -9)(x + -9) = 137

Calculate the square root of the right side: 11.704699911

Break this problem into two subproblems by setting 
(x + -9) equal to 11.704699911 and -11.704699911.

Subproblem 1

x + -9 = 11.704699911 Simplifying x + -9 = 11.704699911 Reorder the terms: -9 + x = 11.704699911 Solving -9 + x = 11.704699911 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '9' to each side of the equation. -9 + 9 + x = 11.704699911 + 9 Combine like terms: -9 + 9 = 0 0 + x = 11.704699911 + 9 x = 11.704699911 + 9 Combine like terms: 11.704699911 + 9 = 20.704699911 x = 20.704699911 Simplifying x = 20.704699911

Subproblem 2

x + -9 = -11.704699911 Simplifying x + -9 = -11.704699911 Reorder the terms: -9 + x = -11.704699911 Solving -9 + x = -11.704699911 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '9' to each side of the equation. -9 + 9 + x = -11.704699911 + 9 Combine like terms: -9 + 9 = 0 0 + x = -11.704699911 + 9 x = -11.704699911 + 9 Combine like terms: -11.704699911 + 9 = -2.704699911 x = -2.704699911 Simplifying x = -2.704699911

Solution

The solution to the problem is based on the solutions from the subproblems. x = {20.704699911, -2.704699911}

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