15r^2-7r-12=

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Solution for 15r^2-7r-12= equation:


Simplifying
15r2 + -7r + -12 = 0

Reorder the terms:
-12 + -7r + 15r2 = 0

Solving
-12 + -7r + 15r2 = 0

Solving for variable 'r'.

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

Divide each side by '15'.
-0.8 + -0.4666666667r + r2 = 0

Move the constant term to the right:

Add '0.8' to each side of the equation.
-0.8 + -0.4666666667r + 0.8 + r2 = 0 + 0.8

Reorder the terms:
-0.8 + 0.8 + -0.4666666667r + r2 = 0 + 0.8

Combine like terms: -0.8 + 0.8 = 0.0
0.0 + -0.4666666667r + r2 = 0 + 0.8
-0.4666666667r + r2 = 0 + 0.8

Combine like terms: 0 + 0.8 = 0.8
-0.4666666667r + r2 = 0.8

The r term is -0.4666666667r.  Take half its coefficient (-0.2333333334).
Square it (0.05444444448) and add it to both sides.

Add '0.05444444448' to each side of the equation.
-0.4666666667r + 0.05444444448 + r2 = 0.8 + 0.05444444448

Reorder the terms:
0.05444444448 + -0.4666666667r + r2 = 0.8 + 0.05444444448

Combine like terms: 0.8 + 0.05444444448 = 0.85444444448
0.05444444448 + -0.4666666667r + r2 = 0.85444444448

Factor a perfect square on the left side:
(r + -0.2333333334)(r + -0.2333333334) = 0.85444444448

Calculate the square root of the right side: 0.924361642

Break this problem into two subproblems by setting 
(r + -0.2333333334) equal to 0.924361642 and -0.924361642.

Subproblem 1

r + -0.2333333334 = 0.924361642 Simplifying r + -0.2333333334 = 0.924361642 Reorder the terms: -0.2333333334 + r = 0.924361642 Solving -0.2333333334 + r = 0.924361642 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '0.2333333334' to each side of the equation. -0.2333333334 + 0.2333333334 + r = 0.924361642 + 0.2333333334 Combine like terms: -0.2333333334 + 0.2333333334 = 0.0000000000 0.0000000000 + r = 0.924361642 + 0.2333333334 r = 0.924361642 + 0.2333333334 Combine like terms: 0.924361642 + 0.2333333334 = 1.1576949754 r = 1.1576949754 Simplifying r = 1.1576949754

Subproblem 2

r + -0.2333333334 = -0.924361642 Simplifying r + -0.2333333334 = -0.924361642 Reorder the terms: -0.2333333334 + r = -0.924361642 Solving -0.2333333334 + r = -0.924361642 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '0.2333333334' to each side of the equation. -0.2333333334 + 0.2333333334 + r = -0.924361642 + 0.2333333334 Combine like terms: -0.2333333334 + 0.2333333334 = 0.0000000000 0.0000000000 + r = -0.924361642 + 0.2333333334 r = -0.924361642 + 0.2333333334 Combine like terms: -0.924361642 + 0.2333333334 = -0.6910283086 r = -0.6910283086 Simplifying r = -0.6910283086

Solution

The solution to the problem is based on the solutions from the subproblems. r = {1.1576949754, -0.6910283086}

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