5r^2+7r-5=12

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Solution for 5r^2+7r-5=12 equation:


Simplifying
5r2 + 7r + -5 = 12

Reorder the terms:
-5 + 7r + 5r2 = 12

Solving
-5 + 7r + 5r2 = 12

Solving for variable 'r'.

Reorder the terms:
-5 + -12 + 7r + 5r2 = 12 + -12

Combine like terms: -5 + -12 = -17
-17 + 7r + 5r2 = 12 + -12

Combine like terms: 12 + -12 = 0
-17 + 7r + 5r2 = 0

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

Divide each side by '5'.
-3.4 + 1.4r + r2 = 0

Move the constant term to the right:

Add '3.4' to each side of the equation.
-3.4 + 1.4r + 3.4 + r2 = 0 + 3.4

Reorder the terms:
-3.4 + 3.4 + 1.4r + r2 = 0 + 3.4

Combine like terms: -3.4 + 3.4 = 0.0
0.0 + 1.4r + r2 = 0 + 3.4
1.4r + r2 = 0 + 3.4

Combine like terms: 0 + 3.4 = 3.4
1.4r + r2 = 3.4

The r term is 1.4r.  Take half its coefficient (0.7).
Square it (0.49) and add it to both sides.

Add '0.49' to each side of the equation.
1.4r + 0.49 + r2 = 3.4 + 0.49

Reorder the terms:
0.49 + 1.4r + r2 = 3.4 + 0.49

Combine like terms: 3.4 + 0.49 = 3.89
0.49 + 1.4r + r2 = 3.89

Factor a perfect square on the left side:
(r + 0.7)(r + 0.7) = 3.89

Calculate the square root of the right side: 1.972308292

Break this problem into two subproblems by setting 
(r + 0.7) equal to 1.972308292 and -1.972308292.

Subproblem 1

r + 0.7 = 1.972308292 Simplifying r + 0.7 = 1.972308292 Reorder the terms: 0.7 + r = 1.972308292 Solving 0.7 + r = 1.972308292 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '-0.7' to each side of the equation. 0.7 + -0.7 + r = 1.972308292 + -0.7 Combine like terms: 0.7 + -0.7 = 0.0 0.0 + r = 1.972308292 + -0.7 r = 1.972308292 + -0.7 Combine like terms: 1.972308292 + -0.7 = 1.272308292 r = 1.272308292 Simplifying r = 1.272308292

Subproblem 2

r + 0.7 = -1.972308292 Simplifying r + 0.7 = -1.972308292 Reorder the terms: 0.7 + r = -1.972308292 Solving 0.7 + r = -1.972308292 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '-0.7' to each side of the equation. 0.7 + -0.7 + r = -1.972308292 + -0.7 Combine like terms: 0.7 + -0.7 = 0.0 0.0 + r = -1.972308292 + -0.7 r = -1.972308292 + -0.7 Combine like terms: -1.972308292 + -0.7 = -2.672308292 r = -2.672308292 Simplifying r = -2.672308292

Solution

The solution to the problem is based on the solutions from the subproblems. r = {1.272308292, -2.672308292}

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