r^2-12r-25=0

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Solution for r^2-12r-25=0 equation:


Simplifying
r2 + -12r + -25 = 0

Reorder the terms:
-25 + -12r + r2 = 0

Solving
-25 + -12r + r2 = 0

Solving for variable 'r'.

Begin completing the square.

Move the constant term to the right:

Add '25' to each side of the equation.
-25 + -12r + 25 + r2 = 0 + 25

Reorder the terms:
-25 + 25 + -12r + r2 = 0 + 25

Combine like terms: -25 + 25 = 0
0 + -12r + r2 = 0 + 25
-12r + r2 = 0 + 25

Combine like terms: 0 + 25 = 25
-12r + r2 = 25

The r term is -12r.  Take half its coefficient (-6).
Square it (36) and add it to both sides.

Add '36' to each side of the equation.
-12r + 36 + r2 = 25 + 36

Reorder the terms:
36 + -12r + r2 = 25 + 36

Combine like terms: 25 + 36 = 61
36 + -12r + r2 = 61

Factor a perfect square on the left side:
(r + -6)(r + -6) = 61

Calculate the square root of the right side: 7.810249676

Break this problem into two subproblems by setting 
(r + -6) equal to 7.810249676 and -7.810249676.

Subproblem 1

r + -6 = 7.810249676 Simplifying r + -6 = 7.810249676 Reorder the terms: -6 + r = 7.810249676 Solving -6 + r = 7.810249676 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '6' to each side of the equation. -6 + 6 + r = 7.810249676 + 6 Combine like terms: -6 + 6 = 0 0 + r = 7.810249676 + 6 r = 7.810249676 + 6 Combine like terms: 7.810249676 + 6 = 13.810249676 r = 13.810249676 Simplifying r = 13.810249676

Subproblem 2

r + -6 = -7.810249676 Simplifying r + -6 = -7.810249676 Reorder the terms: -6 + r = -7.810249676 Solving -6 + r = -7.810249676 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '6' to each side of the equation. -6 + 6 + r = -7.810249676 + 6 Combine like terms: -6 + 6 = 0 0 + r = -7.810249676 + 6 r = -7.810249676 + 6 Combine like terms: -7.810249676 + 6 = -1.810249676 r = -1.810249676 Simplifying r = -1.810249676

Solution

The solution to the problem is based on the solutions from the subproblems. r = {13.810249676, -1.810249676}

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