x^2+25x-81=0

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Solution for x^2+25x-81=0 equation:


Simplifying
x2 + 25x + -81 = 0

Reorder the terms:
-81 + 25x + x2 = 0

Solving
-81 + 25x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '81' to each side of the equation.
-81 + 25x + 81 + x2 = 0 + 81

Reorder the terms:
-81 + 81 + 25x + x2 = 0 + 81

Combine like terms: -81 + 81 = 0
0 + 25x + x2 = 0 + 81
25x + x2 = 0 + 81

Combine like terms: 0 + 81 = 81
25x + x2 = 81

The x term is 25x.  Take half its coefficient (12.5).
Square it (156.25) and add it to both sides.

Add '156.25' to each side of the equation.
25x + 156.25 + x2 = 81 + 156.25

Reorder the terms:
156.25 + 25x + x2 = 81 + 156.25

Combine like terms: 81 + 156.25 = 237.25
156.25 + 25x + x2 = 237.25

Factor a perfect square on the left side:
(x + 12.5)(x + 12.5) = 237.25

Calculate the square root of the right side: 15.402921801

Break this problem into two subproblems by setting 
(x + 12.5) equal to 15.402921801 and -15.402921801.

Subproblem 1

x + 12.5 = 15.402921801 Simplifying x + 12.5 = 15.402921801 Reorder the terms: 12.5 + x = 15.402921801 Solving 12.5 + x = 15.402921801 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-12.5' to each side of the equation. 12.5 + -12.5 + x = 15.402921801 + -12.5 Combine like terms: 12.5 + -12.5 = 0.0 0.0 + x = 15.402921801 + -12.5 x = 15.402921801 + -12.5 Combine like terms: 15.402921801 + -12.5 = 2.902921801 x = 2.902921801 Simplifying x = 2.902921801

Subproblem 2

x + 12.5 = -15.402921801 Simplifying x + 12.5 = -15.402921801 Reorder the terms: 12.5 + x = -15.402921801 Solving 12.5 + x = -15.402921801 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-12.5' to each side of the equation. 12.5 + -12.5 + x = -15.402921801 + -12.5 Combine like terms: 12.5 + -12.5 = 0.0 0.0 + x = -15.402921801 + -12.5 x = -15.402921801 + -12.5 Combine like terms: -15.402921801 + -12.5 = -27.902921801 x = -27.902921801 Simplifying x = -27.902921801

Solution

The solution to the problem is based on the solutions from the subproblems. x = {2.902921801, -27.902921801}

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