103.9r*r+103.9r-31.1=0

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Solution for 103.9r*r+103.9r-31.1=0 equation:


Simplifying
103.9r * r + 103.9r + -31.1 = 0

Multiply r * r
103.9r2 + 103.9r + -31.1 = 0

Reorder the terms:
-31.1 + 103.9r + 103.9r2 = 0

Solving
-31.1 + 103.9r + 103.9r2 = 0

Solving for variable 'r'.

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

Divide each side by '103.9'.
-0.2993262753 + r + r2 = 0

Move the constant term to the right:

Add '0.2993262753' to each side of the equation.
-0.2993262753 + r + 0.2993262753 + r2 = 0 + 0.2993262753

Reorder the terms:
-0.2993262753 + 0.2993262753 + r + r2 = 0 + 0.2993262753

Combine like terms: -0.2993262753 + 0.2993262753 = 0.0000000000
0.0000000000 + r + r2 = 0 + 0.2993262753
r + r2 = 0 + 0.2993262753

Combine like terms: 0 + 0.2993262753 = 0.2993262753
r + r2 = 0.2993262753

The r term is r.  Take half its coefficient (0.5).
Square it (0.25) and add it to both sides.

Add '0.25' to each side of the equation.
 + 0.25 + r2 = 0.2993262753 + 0.25

Combine like terms:  + 0.25 = 1.25
1.25 + r2 = 0.2993262753 + 0.25

Combine like terms: 0.2993262753 + 0.25 = 0.5493262753
1.25 + r2 = 0.5493262753

Factor a perfect square on the left side:
(r + 0.5)(r + 0.5) = 0.5493262753

Calculate the square root of the right side: 0.741165484

Break this problem into two subproblems by setting 
(r + 0.5) equal to 0.741165484 and -0.741165484.

Subproblem 1

r + 0.5 = 0.741165484 Simplifying r + 0.5 = 0.741165484 Reorder the terms: 0.5 + r = 0.741165484 Solving 0.5 + r = 0.741165484 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '-0.5' to each side of the equation. 0.5 + -0.5 + r = 0.741165484 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + r = 0.741165484 + -0.5 r = 0.741165484 + -0.5 Combine like terms: 0.741165484 + -0.5 = 0.241165484 r = 0.241165484 Simplifying r = 0.241165484

Subproblem 2

r + 0.5 = -0.741165484 Simplifying r + 0.5 = -0.741165484 Reorder the terms: 0.5 + r = -0.741165484 Solving 0.5 + r = -0.741165484 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '-0.5' to each side of the equation. 0.5 + -0.5 + r = -0.741165484 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + r = -0.741165484 + -0.5 r = -0.741165484 + -0.5 Combine like terms: -0.741165484 + -0.5 = -1.241165484 r = -1.241165484 Simplifying r = -1.241165484

Solution

The solution to the problem is based on the solutions from the subproblems. r = {0.241165484, -1.241165484}

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