5r^2-2r=12

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Solution for 5r^2-2r=12 equation:


Simplifying
5r2 + -2r = 12

Reorder the terms:
-2r + 5r2 = 12

Solving
-2r + 5r2 = 12

Solving for variable 'r'.

Reorder the terms:
-12 + -2r + 5r2 = 12 + -12

Combine like terms: 12 + -12 = 0
-12 + -2r + 5r2 = 0

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

Divide each side by '5'.
-2.4 + -0.4r + r2 = 0

Move the constant term to the right:

Add '2.4' to each side of the equation.
-2.4 + -0.4r + 2.4 + r2 = 0 + 2.4

Reorder the terms:
-2.4 + 2.4 + -0.4r + r2 = 0 + 2.4

Combine like terms: -2.4 + 2.4 = 0.0
0.0 + -0.4r + r2 = 0 + 2.4
-0.4r + r2 = 0 + 2.4

Combine like terms: 0 + 2.4 = 2.4
-0.4r + r2 = 2.4

The r term is -0.4r.  Take half its coefficient (-0.2).
Square it (0.04) and add it to both sides.

Add '0.04' to each side of the equation.
-0.4r + 0.04 + r2 = 2.4 + 0.04

Reorder the terms:
0.04 + -0.4r + r2 = 2.4 + 0.04

Combine like terms: 2.4 + 0.04 = 2.44
0.04 + -0.4r + r2 = 2.44

Factor a perfect square on the left side:
(r + -0.2)(r + -0.2) = 2.44

Calculate the square root of the right side: 1.562049935

Break this problem into two subproblems by setting 
(r + -0.2) equal to 1.562049935 and -1.562049935.

Subproblem 1

r + -0.2 = 1.562049935 Simplifying r + -0.2 = 1.562049935 Reorder the terms: -0.2 + r = 1.562049935 Solving -0.2 + r = 1.562049935 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '0.2' to each side of the equation. -0.2 + 0.2 + r = 1.562049935 + 0.2 Combine like terms: -0.2 + 0.2 = 0.0 0.0 + r = 1.562049935 + 0.2 r = 1.562049935 + 0.2 Combine like terms: 1.562049935 + 0.2 = 1.762049935 r = 1.762049935 Simplifying r = 1.762049935

Subproblem 2

r + -0.2 = -1.562049935 Simplifying r + -0.2 = -1.562049935 Reorder the terms: -0.2 + r = -1.562049935 Solving -0.2 + r = -1.562049935 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '0.2' to each side of the equation. -0.2 + 0.2 + r = -1.562049935 + 0.2 Combine like terms: -0.2 + 0.2 = 0.0 0.0 + r = -1.562049935 + 0.2 r = -1.562049935 + 0.2 Combine like terms: -1.562049935 + 0.2 = -1.362049935 r = -1.362049935 Simplifying r = -1.362049935

Solution

The solution to the problem is based on the solutions from the subproblems. r = {1.762049935, -1.362049935}

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