r^2+12r-128=0

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Solution for r^2+12r-128=0 equation:


Simplifying
r2 + 12r + -128 = 0

Reorder the terms:
-128 + 12r + r2 = 0

Solving
-128 + 12r + r2 = 0

Solving for variable 'r'.

Begin completing the square.

Move the constant term to the right:

Add '128' to each side of the equation.
-128 + 12r + 128 + r2 = 0 + 128

Reorder the terms:
-128 + 128 + 12r + r2 = 0 + 128

Combine like terms: -128 + 128 = 0
0 + 12r + r2 = 0 + 128
12r + r2 = 0 + 128

Combine like terms: 0 + 128 = 128
12r + r2 = 128

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 = 128 + 36

Reorder the terms:
36 + 12r + r2 = 128 + 36

Combine like terms: 128 + 36 = 164
36 + 12r + r2 = 164

Factor a perfect square on the left side:
(r + 6)(r + 6) = 164

Calculate the square root of the right side: 12.806248475

Break this problem into two subproblems by setting 
(r + 6) equal to 12.806248475 and -12.806248475.

Subproblem 1

r + 6 = 12.806248475 Simplifying r + 6 = 12.806248475 Reorder the terms: 6 + r = 12.806248475 Solving 6 + r = 12.806248475 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 = 12.806248475 + -6 Combine like terms: 6 + -6 = 0 0 + r = 12.806248475 + -6 r = 12.806248475 + -6 Combine like terms: 12.806248475 + -6 = 6.806248475 r = 6.806248475 Simplifying r = 6.806248475

Subproblem 2

r + 6 = -12.806248475 Simplifying r + 6 = -12.806248475 Reorder the terms: 6 + r = -12.806248475 Solving 6 + r = -12.806248475 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 = -12.806248475 + -6 Combine like terms: 6 + -6 = 0 0 + r = -12.806248475 + -6 r = -12.806248475 + -6 Combine like terms: -12.806248475 + -6 = -18.806248475 r = -18.806248475 Simplifying r = -18.806248475

Solution

The solution to the problem is based on the solutions from the subproblems. r = {6.806248475, -18.806248475}

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