r^2+10r-55=0

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Solution for r^2+10r-55=0 equation:


Simplifying
r2 + 10r + -55 = 0

Reorder the terms:
-55 + 10r + r2 = 0

Solving
-55 + 10r + r2 = 0

Solving for variable 'r'.

Begin completing the square.

Move the constant term to the right:

Add '55' to each side of the equation.
-55 + 10r + 55 + r2 = 0 + 55

Reorder the terms:
-55 + 55 + 10r + r2 = 0 + 55

Combine like terms: -55 + 55 = 0
0 + 10r + r2 = 0 + 55
10r + r2 = 0 + 55

Combine like terms: 0 + 55 = 55
10r + r2 = 55

The r term is 10r.  Take half its coefficient (5).
Square it (25) and add it to both sides.

Add '25' to each side of the equation.
10r + 25 + r2 = 55 + 25

Reorder the terms:
25 + 10r + r2 = 55 + 25

Combine like terms: 55 + 25 = 80
25 + 10r + r2 = 80

Factor a perfect square on the left side:
(r + 5)(r + 5) = 80

Calculate the square root of the right side: 8.94427191

Break this problem into two subproblems by setting 
(r + 5) equal to 8.94427191 and -8.94427191.

Subproblem 1

r + 5 = 8.94427191 Simplifying r + 5 = 8.94427191 Reorder the terms: 5 + r = 8.94427191 Solving 5 + r = 8.94427191 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '-5' to each side of the equation. 5 + -5 + r = 8.94427191 + -5 Combine like terms: 5 + -5 = 0 0 + r = 8.94427191 + -5 r = 8.94427191 + -5 Combine like terms: 8.94427191 + -5 = 3.94427191 r = 3.94427191 Simplifying r = 3.94427191

Subproblem 2

r + 5 = -8.94427191 Simplifying r + 5 = -8.94427191 Reorder the terms: 5 + r = -8.94427191 Solving 5 + r = -8.94427191 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '-5' to each side of the equation. 5 + -5 + r = -8.94427191 + -5 Combine like terms: 5 + -5 = 0 0 + r = -8.94427191 + -5 r = -8.94427191 + -5 Combine like terms: -8.94427191 + -5 = -13.94427191 r = -13.94427191 Simplifying r = -13.94427191

Solution

The solution to the problem is based on the solutions from the subproblems. r = {3.94427191, -13.94427191}

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