5r^2-7=12r

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Solution for 5r^2-7=12r equation:


Simplifying
5r2 + -7 = 12r

Reorder the terms:
-7 + 5r2 = 12r

Solving
-7 + 5r2 = 12r

Solving for variable 'r'.

Reorder the terms:
-7 + -12r + 5r2 = 12r + -12r

Combine like terms: 12r + -12r = 0
-7 + -12r + 5r2 = 0

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

Divide each side by '5'.
-1.4 + -2.4r + r2 = 0

Move the constant term to the right:

Add '1.4' to each side of the equation.
-1.4 + -2.4r + 1.4 + r2 = 0 + 1.4

Reorder the terms:
-1.4 + 1.4 + -2.4r + r2 = 0 + 1.4

Combine like terms: -1.4 + 1.4 = 0.0
0.0 + -2.4r + r2 = 0 + 1.4
-2.4r + r2 = 0 + 1.4

Combine like terms: 0 + 1.4 = 1.4
-2.4r + r2 = 1.4

The r term is -2.4r.  Take half its coefficient (-1.2).
Square it (1.44) and add it to both sides.

Add '1.44' to each side of the equation.
-2.4r + 1.44 + r2 = 1.4 + 1.44

Reorder the terms:
1.44 + -2.4r + r2 = 1.4 + 1.44

Combine like terms: 1.4 + 1.44 = 2.84
1.44 + -2.4r + r2 = 2.84

Factor a perfect square on the left side:
(r + -1.2)(r + -1.2) = 2.84

Calculate the square root of the right side: 1.685229955

Break this problem into two subproblems by setting 
(r + -1.2) equal to 1.685229955 and -1.685229955.

Subproblem 1

r + -1.2 = 1.685229955 Simplifying r + -1.2 = 1.685229955 Reorder the terms: -1.2 + r = 1.685229955 Solving -1.2 + r = 1.685229955 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '1.2' to each side of the equation. -1.2 + 1.2 + r = 1.685229955 + 1.2 Combine like terms: -1.2 + 1.2 = 0.0 0.0 + r = 1.685229955 + 1.2 r = 1.685229955 + 1.2 Combine like terms: 1.685229955 + 1.2 = 2.885229955 r = 2.885229955 Simplifying r = 2.885229955

Subproblem 2

r + -1.2 = -1.685229955 Simplifying r + -1.2 = -1.685229955 Reorder the terms: -1.2 + r = -1.685229955 Solving -1.2 + r = -1.685229955 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '1.2' to each side of the equation. -1.2 + 1.2 + r = -1.685229955 + 1.2 Combine like terms: -1.2 + 1.2 = 0.0 0.0 + r = -1.685229955 + 1.2 r = -1.685229955 + 1.2 Combine like terms: -1.685229955 + 1.2 = -0.485229955 r = -0.485229955 Simplifying r = -0.485229955

Solution

The solution to the problem is based on the solutions from the subproblems. r = {2.885229955, -0.485229955}

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