13r^2+20r+100=0

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Solution for 13r^2+20r+100=0 equation:


Simplifying
13r2 + 20r + 100 = 0

Reorder the terms:
100 + 20r + 13r2 = 0

Solving
100 + 20r + 13r2 = 0

Solving for variable 'r'.

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

Divide each side by '13'.
7.692307692 + 1.538461538r + r2 = 0

Move the constant term to the right:

Add '-7.692307692' to each side of the equation.
7.692307692 + 1.538461538r + -7.692307692 + r2 = 0 + -7.692307692

Reorder the terms:
7.692307692 + -7.692307692 + 1.538461538r + r2 = 0 + -7.692307692

Combine like terms: 7.692307692 + -7.692307692 = 0.000000000
0.000000000 + 1.538461538r + r2 = 0 + -7.692307692
1.538461538r + r2 = 0 + -7.692307692

Combine like terms: 0 + -7.692307692 = -7.692307692
1.538461538r + r2 = -7.692307692

The r term is 1.538461538r.  Take half its coefficient (0.769230769).
Square it (0.5917159760) and add it to both sides.

Add '0.5917159760' to each side of the equation.
1.538461538r + 0.5917159760 + r2 = -7.692307692 + 0.5917159760

Reorder the terms:
0.5917159760 + 1.538461538r + r2 = -7.692307692 + 0.5917159760

Combine like terms: -7.692307692 + 0.5917159760 = -7.100591716
0.5917159760 + 1.538461538r + r2 = -7.100591716

Factor a perfect square on the left side:
(r + 0.769230769)(r + 0.769230769) = -7.100591716

Can't calculate square root of the right side.

The solution to this equation could not be determined.

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