-7r^2+140r+100=0

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Solution for -7r^2+140r+100=0 equation:


Simplifying
-7r2 + 140r + 100 = 0

Reorder the terms:
100 + 140r + -7r2 = 0

Solving
100 + 140r + -7r2 = 0

Solving for variable 'r'.

Begin completing the square.  Divide all terms by
-7 the coefficient of the squared term: 

Divide each side by '-7'.
-14.28571429 + -20r + r2 = 0

Move the constant term to the right:

Add '14.28571429' to each side of the equation.
-14.28571429 + -20r + 14.28571429 + r2 = 0 + 14.28571429

Reorder the terms:
-14.28571429 + 14.28571429 + -20r + r2 = 0 + 14.28571429

Combine like terms: -14.28571429 + 14.28571429 = 0.00000000
0.00000000 + -20r + r2 = 0 + 14.28571429
-20r + r2 = 0 + 14.28571429

Combine like terms: 0 + 14.28571429 = 14.28571429
-20r + r2 = 14.28571429

The r term is -20r.  Take half its coefficient (-10).
Square it (100) and add it to both sides.

Add '100' to each side of the equation.
-20r + 100 + r2 = 14.28571429 + 100

Reorder the terms:
100 + -20r + r2 = 14.28571429 + 100

Combine like terms: 14.28571429 + 100 = 114.28571429
100 + -20r + r2 = 114.28571429

Factor a perfect square on the left side:
(r + -10)(r + -10) = 114.28571429

Calculate the square root of the right side: 10.690449677

Break this problem into two subproblems by setting 
(r + -10) equal to 10.690449677 and -10.690449677.

Subproblem 1

r + -10 = 10.690449677 Simplifying r + -10 = 10.690449677 Reorder the terms: -10 + r = 10.690449677 Solving -10 + r = 10.690449677 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '10' to each side of the equation. -10 + 10 + r = 10.690449677 + 10 Combine like terms: -10 + 10 = 0 0 + r = 10.690449677 + 10 r = 10.690449677 + 10 Combine like terms: 10.690449677 + 10 = 20.690449677 r = 20.690449677 Simplifying r = 20.690449677

Subproblem 2

r + -10 = -10.690449677 Simplifying r + -10 = -10.690449677 Reorder the terms: -10 + r = -10.690449677 Solving -10 + r = -10.690449677 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '10' to each side of the equation. -10 + 10 + r = -10.690449677 + 10 Combine like terms: -10 + 10 = 0 0 + r = -10.690449677 + 10 r = -10.690449677 + 10 Combine like terms: -10.690449677 + 10 = -0.690449677 r = -0.690449677 Simplifying r = -0.690449677

Solution

The solution to the problem is based on the solutions from the subproblems. r = {20.690449677, -0.690449677}

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