15=x+5x^2

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Solution for 15=x+5x^2 equation:


Simplifying
15 = x + 5x2

Solving
15 = x + 5x2

Solving for variable 'x'.

Reorder the terms:
15 + -1x + -5x2 = x + -1x + 5x2 + -5x2

Combine like terms: x + -1x = 0
15 + -1x + -5x2 = 0 + 5x2 + -5x2
15 + -1x + -5x2 = 5x2 + -5x2

Combine like terms: 5x2 + -5x2 = 0
15 + -1x + -5x2 = 0

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

Divide each side by '-5'.
-3 + 0.2x + x2 = 0

Move the constant term to the right:

Add '3' to each side of the equation.
-3 + 0.2x + 3 + x2 = 0 + 3

Reorder the terms:
-3 + 3 + 0.2x + x2 = 0 + 3

Combine like terms: -3 + 3 = 0
0 + 0.2x + x2 = 0 + 3
0.2x + x2 = 0 + 3

Combine like terms: 0 + 3 = 3
0.2x + x2 = 3

The x term is 0.2x.  Take half its coefficient (0.1).
Square it (0.01) and add it to both sides.

Add '0.01' to each side of the equation.
0.2x + 0.01 + x2 = 3 + 0.01

Reorder the terms:
0.01 + 0.2x + x2 = 3 + 0.01

Combine like terms: 3 + 0.01 = 3.01
0.01 + 0.2x + x2 = 3.01

Factor a perfect square on the left side:
(x + 0.1)(x + 0.1) = 3.01

Calculate the square root of the right side: 1.734935157

Break this problem into two subproblems by setting 
(x + 0.1) equal to 1.734935157 and -1.734935157.

Subproblem 1

x + 0.1 = 1.734935157 Simplifying x + 0.1 = 1.734935157 Reorder the terms: 0.1 + x = 1.734935157 Solving 0.1 + x = 1.734935157 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.1' to each side of the equation. 0.1 + -0.1 + x = 1.734935157 + -0.1 Combine like terms: 0.1 + -0.1 = 0.0 0.0 + x = 1.734935157 + -0.1 x = 1.734935157 + -0.1 Combine like terms: 1.734935157 + -0.1 = 1.634935157 x = 1.634935157 Simplifying x = 1.634935157

Subproblem 2

x + 0.1 = -1.734935157 Simplifying x + 0.1 = -1.734935157 Reorder the terms: 0.1 + x = -1.734935157 Solving 0.1 + x = -1.734935157 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.1' to each side of the equation. 0.1 + -0.1 + x = -1.734935157 + -0.1 Combine like terms: 0.1 + -0.1 = 0.0 0.0 + x = -1.734935157 + -0.1 x = -1.734935157 + -0.1 Combine like terms: -1.734935157 + -0.1 = -1.834935157 x = -1.834935157 Simplifying x = -1.834935157

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.634935157, -1.834935157}

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