9r^2-18r-69=4

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Solution for 9r^2-18r-69=4 equation:


Simplifying
9r2 + -18r + -69 = 4

Reorder the terms:
-69 + -18r + 9r2 = 4

Solving
-69 + -18r + 9r2 = 4

Solving for variable 'r'.

Reorder the terms:
-69 + -4 + -18r + 9r2 = 4 + -4

Combine like terms: -69 + -4 = -73
-73 + -18r + 9r2 = 4 + -4

Combine like terms: 4 + -4 = 0
-73 + -18r + 9r2 = 0

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

Divide each side by '9'.
-8.111111111 + -2r + r2 = 0

Move the constant term to the right:

Add '8.111111111' to each side of the equation.
-8.111111111 + -2r + 8.111111111 + r2 = 0 + 8.111111111

Reorder the terms:
-8.111111111 + 8.111111111 + -2r + r2 = 0 + 8.111111111

Combine like terms: -8.111111111 + 8.111111111 = 0.000000000
0.000000000 + -2r + r2 = 0 + 8.111111111
-2r + r2 = 0 + 8.111111111

Combine like terms: 0 + 8.111111111 = 8.111111111
-2r + r2 = 8.111111111

The r term is -2r.  Take half its coefficient (-1).
Square it (1) and add it to both sides.

Add '1' to each side of the equation.
-2r + 1 + r2 = 8.111111111 + 1

Reorder the terms:
1 + -2r + r2 = 8.111111111 + 1

Combine like terms: 8.111111111 + 1 = 9.111111111
1 + -2r + r2 = 9.111111111

Factor a perfect square on the left side:
(r + -1)(r + -1) = 9.111111111

Calculate the square root of the right side: 3.018461713

Break this problem into two subproblems by setting 
(r + -1) equal to 3.018461713 and -3.018461713.

Subproblem 1

r + -1 = 3.018461713 Simplifying r + -1 = 3.018461713 Reorder the terms: -1 + r = 3.018461713 Solving -1 + r = 3.018461713 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '1' to each side of the equation. -1 + 1 + r = 3.018461713 + 1 Combine like terms: -1 + 1 = 0 0 + r = 3.018461713 + 1 r = 3.018461713 + 1 Combine like terms: 3.018461713 + 1 = 4.018461713 r = 4.018461713 Simplifying r = 4.018461713

Subproblem 2

r + -1 = -3.018461713 Simplifying r + -1 = -3.018461713 Reorder the terms: -1 + r = -3.018461713 Solving -1 + r = -3.018461713 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '1' to each side of the equation. -1 + 1 + r = -3.018461713 + 1 Combine like terms: -1 + 1 = 0 0 + r = -3.018461713 + 1 r = -3.018461713 + 1 Combine like terms: -3.018461713 + 1 = -2.018461713 r = -2.018461713 Simplifying r = -2.018461713

Solution

The solution to the problem is based on the solutions from the subproblems. r = {4.018461713, -2.018461713}

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