7r+2=5r(r-4)

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Solution for 7r+2=5r(r-4) equation:


Simplifying
7r + 2 = 5r(r + -4)

Reorder the terms:
2 + 7r = 5r(r + -4)

Reorder the terms:
2 + 7r = 5r(-4 + r)
2 + 7r = (-4 * 5r + r * 5r)
2 + 7r = (-20r + 5r2)

Solving
2 + 7r = -20r + 5r2

Solving for variable 'r'.

Combine like terms: 7r + 20r = 27r
2 + 27r + -5r2 = -20r + 5r2 + 20r + -5r2

Reorder the terms:
2 + 27r + -5r2 = -20r + 20r + 5r2 + -5r2

Combine like terms: -20r + 20r = 0
2 + 27r + -5r2 = 0 + 5r2 + -5r2
2 + 27r + -5r2 = 5r2 + -5r2

Combine like terms: 5r2 + -5r2 = 0
2 + 27r + -5r2 = 0

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

Divide each side by '-5'.
-0.4 + -5.4r + r2 = 0

Move the constant term to the right:

Add '0.4' to each side of the equation.
-0.4 + -5.4r + 0.4 + r2 = 0 + 0.4

Reorder the terms:
-0.4 + 0.4 + -5.4r + r2 = 0 + 0.4

Combine like terms: -0.4 + 0.4 = 0.0
0.0 + -5.4r + r2 = 0 + 0.4
-5.4r + r2 = 0 + 0.4

Combine like terms: 0 + 0.4 = 0.4
-5.4r + r2 = 0.4

The r term is -5.4r.  Take half its coefficient (-2.7).
Square it (7.29) and add it to both sides.

Add '7.29' to each side of the equation.
-5.4r + 7.29 + r2 = 0.4 + 7.29

Reorder the terms:
7.29 + -5.4r + r2 = 0.4 + 7.29

Combine like terms: 0.4 + 7.29 = 7.69
7.29 + -5.4r + r2 = 7.69

Factor a perfect square on the left side:
(r + -2.7)(r + -2.7) = 7.69

Calculate the square root of the right side: 2.773084925

Break this problem into two subproblems by setting 
(r + -2.7) equal to 2.773084925 and -2.773084925.

Subproblem 1

r + -2.7 = 2.773084925 Simplifying r + -2.7 = 2.773084925 Reorder the terms: -2.7 + r = 2.773084925 Solving -2.7 + r = 2.773084925 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '2.7' to each side of the equation. -2.7 + 2.7 + r = 2.773084925 + 2.7 Combine like terms: -2.7 + 2.7 = 0.0 0.0 + r = 2.773084925 + 2.7 r = 2.773084925 + 2.7 Combine like terms: 2.773084925 + 2.7 = 5.473084925 r = 5.473084925 Simplifying r = 5.473084925

Subproblem 2

r + -2.7 = -2.773084925 Simplifying r + -2.7 = -2.773084925 Reorder the terms: -2.7 + r = -2.773084925 Solving -2.7 + r = -2.773084925 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '2.7' to each side of the equation. -2.7 + 2.7 + r = -2.773084925 + 2.7 Combine like terms: -2.7 + 2.7 = 0.0 0.0 + r = -2.773084925 + 2.7 r = -2.773084925 + 2.7 Combine like terms: -2.773084925 + 2.7 = -0.073084925 r = -0.073084925 Simplifying r = -0.073084925

Solution

The solution to the problem is based on the solutions from the subproblems. r = {5.473084925, -0.073084925}

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