5r(r+6)-9=

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Solution for 5r(r+6)-9= equation:


Simplifying
5r(r + 6) + -9 = 0

Reorder the terms:
5r(6 + r) + -9 = 0
(6 * 5r + r * 5r) + -9 = 0
(30r + 5r2) + -9 = 0

Reorder the terms:
-9 + 30r + 5r2 = 0

Solving
-9 + 30r + 5r2 = 0

Solving for variable 'r'.

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

Divide each side by '5'.
-1.8 + 6r + r2 = 0

Move the constant term to the right:

Add '1.8' to each side of the equation.
-1.8 + 6r + 1.8 + r2 = 0 + 1.8

Reorder the terms:
-1.8 + 1.8 + 6r + r2 = 0 + 1.8

Combine like terms: -1.8 + 1.8 = 0.0
0.0 + 6r + r2 = 0 + 1.8
6r + r2 = 0 + 1.8

Combine like terms: 0 + 1.8 = 1.8
6r + r2 = 1.8

The r term is 6r.  Take half its coefficient (3).
Square it (9) and add it to both sides.

Add '9' to each side of the equation.
6r + 9 + r2 = 1.8 + 9

Reorder the terms:
9 + 6r + r2 = 1.8 + 9

Combine like terms: 1.8 + 9 = 10.8
9 + 6r + r2 = 10.8

Factor a perfect square on the left side:
(r + 3)(r + 3) = 10.8

Calculate the square root of the right side: 3.286335345

Break this problem into two subproblems by setting 
(r + 3) equal to 3.286335345 and -3.286335345.

Subproblem 1

r + 3 = 3.286335345 Simplifying r + 3 = 3.286335345 Reorder the terms: 3 + r = 3.286335345 Solving 3 + r = 3.286335345 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '-3' to each side of the equation. 3 + -3 + r = 3.286335345 + -3 Combine like terms: 3 + -3 = 0 0 + r = 3.286335345 + -3 r = 3.286335345 + -3 Combine like terms: 3.286335345 + -3 = 0.286335345 r = 0.286335345 Simplifying r = 0.286335345

Subproblem 2

r + 3 = -3.286335345 Simplifying r + 3 = -3.286335345 Reorder the terms: 3 + r = -3.286335345 Solving 3 + r = -3.286335345 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '-3' to each side of the equation. 3 + -3 + r = -3.286335345 + -3 Combine like terms: 3 + -3 = 0 0 + r = -3.286335345 + -3 r = -3.286335345 + -3 Combine like terms: -3.286335345 + -3 = -6.286335345 r = -6.286335345 Simplifying r = -6.286335345

Solution

The solution to the problem is based on the solutions from the subproblems. r = {0.286335345, -6.286335345}

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