-3r^2-5r=-7

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Solution for -3r^2-5r=-7 equation:


Simplifying
-3r2 + -5r = -7

Reorder the terms:
-5r + -3r2 = -7

Solving
-5r + -3r2 = -7

Solving for variable 'r'.

Reorder the terms:
7 + -5r + -3r2 = -7 + 7

Combine like terms: -7 + 7 = 0
7 + -5r + -3r2 = 0

Begin completing the square.  Divide all terms by
-3 the coefficient of the squared term: 

Divide each side by '-3'.
-2.333333333 + 1.666666667r + r2 = 0

Move the constant term to the right:

Add '2.333333333' to each side of the equation.
-2.333333333 + 1.666666667r + 2.333333333 + r2 = 0 + 2.333333333

Reorder the terms:
-2.333333333 + 2.333333333 + 1.666666667r + r2 = 0 + 2.333333333

Combine like terms: -2.333333333 + 2.333333333 = 0.000000000
0.000000000 + 1.666666667r + r2 = 0 + 2.333333333
1.666666667r + r2 = 0 + 2.333333333

Combine like terms: 0 + 2.333333333 = 2.333333333
1.666666667r + r2 = 2.333333333

The r term is 1.666666667r.  Take half its coefficient (0.8333333335).
Square it (0.6944444447) and add it to both sides.

Add '0.6944444447' to each side of the equation.
1.666666667r + 0.6944444447 + r2 = 2.333333333 + 0.6944444447

Reorder the terms:
0.6944444447 + 1.666666667r + r2 = 2.333333333 + 0.6944444447

Combine like terms: 2.333333333 + 0.6944444447 = 3.0277777777
0.6944444447 + 1.666666667r + r2 = 3.0277777777

Factor a perfect square on the left side:
(r + 0.8333333335)(r + 0.8333333335) = 3.0277777777

Calculate the square root of the right side: 1.740051085

Break this problem into two subproblems by setting 
(r + 0.8333333335) equal to 1.740051085 and -1.740051085.

Subproblem 1

r + 0.8333333335 = 1.740051085 Simplifying r + 0.8333333335 = 1.740051085 Reorder the terms: 0.8333333335 + r = 1.740051085 Solving 0.8333333335 + r = 1.740051085 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '-0.8333333335' to each side of the equation. 0.8333333335 + -0.8333333335 + r = 1.740051085 + -0.8333333335 Combine like terms: 0.8333333335 + -0.8333333335 = 0.0000000000 0.0000000000 + r = 1.740051085 + -0.8333333335 r = 1.740051085 + -0.8333333335 Combine like terms: 1.740051085 + -0.8333333335 = 0.9067177515 r = 0.9067177515 Simplifying r = 0.9067177515

Subproblem 2

r + 0.8333333335 = -1.740051085 Simplifying r + 0.8333333335 = -1.740051085 Reorder the terms: 0.8333333335 + r = -1.740051085 Solving 0.8333333335 + r = -1.740051085 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '-0.8333333335' to each side of the equation. 0.8333333335 + -0.8333333335 + r = -1.740051085 + -0.8333333335 Combine like terms: 0.8333333335 + -0.8333333335 = 0.0000000000 0.0000000000 + r = -1.740051085 + -0.8333333335 r = -1.740051085 + -0.8333333335 Combine like terms: -1.740051085 + -0.8333333335 = -2.5733844185 r = -2.5733844185 Simplifying r = -2.5733844185

Solution

The solution to the problem is based on the solutions from the subproblems. r = {0.9067177515, -2.5733844185}

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