(r-2)(r+12)=26

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Solution for (r-2)(r+12)=26 equation:


Simplifying
(r + -2)(r + 12) = 26

Reorder the terms:
(-2 + r)(r + 12) = 26

Reorder the terms:
(-2 + r)(12 + r) = 26

Multiply (-2 + r) * (12 + r)
(-2(12 + r) + r(12 + r)) = 26
((12 * -2 + r * -2) + r(12 + r)) = 26
((-24 + -2r) + r(12 + r)) = 26
(-24 + -2r + (12 * r + r * r)) = 26
(-24 + -2r + (12r + r2)) = 26

Combine like terms: -2r + 12r = 10r
(-24 + 10r + r2) = 26

Solving
-24 + 10r + r2 = 26

Solving for variable 'r'.

Reorder the terms:
-24 + -26 + 10r + r2 = 26 + -26

Combine like terms: -24 + -26 = -50
-50 + 10r + r2 = 26 + -26

Combine like terms: 26 + -26 = 0
-50 + 10r + r2 = 0

Begin completing the square.

Move the constant term to the right:

Add '50' to each side of the equation.
-50 + 10r + 50 + r2 = 0 + 50

Reorder the terms:
-50 + 50 + 10r + r2 = 0 + 50

Combine like terms: -50 + 50 = 0
0 + 10r + r2 = 0 + 50
10r + r2 = 0 + 50

Combine like terms: 0 + 50 = 50
10r + r2 = 50

The r term is 10r.  Take half its coefficient (5).
Square it (25) and add it to both sides.

Add '25' to each side of the equation.
10r + 25 + r2 = 50 + 25

Reorder the terms:
25 + 10r + r2 = 50 + 25

Combine like terms: 50 + 25 = 75
25 + 10r + r2 = 75

Factor a perfect square on the left side:
(r + 5)(r + 5) = 75

Calculate the square root of the right side: 8.660254038

Break this problem into two subproblems by setting 
(r + 5) equal to 8.660254038 and -8.660254038.

Subproblem 1

r + 5 = 8.660254038 Simplifying r + 5 = 8.660254038 Reorder the terms: 5 + r = 8.660254038 Solving 5 + r = 8.660254038 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '-5' to each side of the equation. 5 + -5 + r = 8.660254038 + -5 Combine like terms: 5 + -5 = 0 0 + r = 8.660254038 + -5 r = 8.660254038 + -5 Combine like terms: 8.660254038 + -5 = 3.660254038 r = 3.660254038 Simplifying r = 3.660254038

Subproblem 2

r + 5 = -8.660254038 Simplifying r + 5 = -8.660254038 Reorder the terms: 5 + r = -8.660254038 Solving 5 + r = -8.660254038 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '-5' to each side of the equation. 5 + -5 + r = -8.660254038 + -5 Combine like terms: 5 + -5 = 0 0 + r = -8.660254038 + -5 r = -8.660254038 + -5 Combine like terms: -8.660254038 + -5 = -13.660254038 r = -13.660254038 Simplifying r = -13.660254038

Solution

The solution to the problem is based on the solutions from the subproblems. r = {3.660254038, -13.660254038}

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