15=x*x+x*2-1

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Solution for 15=x*x+x*2-1 equation:


Simplifying
15 = x * x + x * 2 + -1

Multiply x * x
15 = x2 + x * 2 + -1

Reorder the terms for easier multiplication:
15 = x2 + 2x + -1

Reorder the terms:
15 = -1 + 2x + x2

Solving
15 = -1 + 2x + x2

Solving for variable 'x'.

Combine like terms: 15 + 1 = 16
16 + -2x + -1x2 = -1 + 2x + x2 + 1 + -2x + -1x2

Reorder the terms:
16 + -2x + -1x2 = -1 + 1 + 2x + -2x + x2 + -1x2

Combine like terms: -1 + 1 = 0
16 + -2x + -1x2 = 0 + 2x + -2x + x2 + -1x2
16 + -2x + -1x2 = 2x + -2x + x2 + -1x2

Combine like terms: 2x + -2x = 0
16 + -2x + -1x2 = 0 + x2 + -1x2
16 + -2x + -1x2 = x2 + -1x2

Combine like terms: x2 + -1x2 = 0
16 + -2x + -1x2 = 0

Begin completing the square.  Divide all terms by
-1 the coefficient of the squared term: 

Divide each side by '-1'.
-16 + 2x + x2 = 0

Move the constant term to the right:

Add '16' to each side of the equation.
-16 + 2x + 16 + x2 = 0 + 16

Reorder the terms:
-16 + 16 + 2x + x2 = 0 + 16

Combine like terms: -16 + 16 = 0
0 + 2x + x2 = 0 + 16
2x + x2 = 0 + 16

Combine like terms: 0 + 16 = 16
2x + x2 = 16

The x term is 2x.  Take half its coefficient (1).
Square it (1) and add it to both sides.

Add '1' to each side of the equation.
2x + 1 + x2 = 16 + 1

Reorder the terms:
1 + 2x + x2 = 16 + 1

Combine like terms: 16 + 1 = 17
1 + 2x + x2 = 17

Factor a perfect square on the left side:
(x + 1)(x + 1) = 17

Calculate the square root of the right side: 4.123105626

Break this problem into two subproblems by setting 
(x + 1) equal to 4.123105626 and -4.123105626.

Subproblem 1

x + 1 = 4.123105626 Simplifying x + 1 = 4.123105626 Reorder the terms: 1 + x = 4.123105626 Solving 1 + x = 4.123105626 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1' to each side of the equation. 1 + -1 + x = 4.123105626 + -1 Combine like terms: 1 + -1 = 0 0 + x = 4.123105626 + -1 x = 4.123105626 + -1 Combine like terms: 4.123105626 + -1 = 3.123105626 x = 3.123105626 Simplifying x = 3.123105626

Subproblem 2

x + 1 = -4.123105626 Simplifying x + 1 = -4.123105626 Reorder the terms: 1 + x = -4.123105626 Solving 1 + x = -4.123105626 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1' to each side of the equation. 1 + -1 + x = -4.123105626 + -1 Combine like terms: 1 + -1 = 0 0 + x = -4.123105626 + -1 x = -4.123105626 + -1 Combine like terms: -4.123105626 + -1 = -5.123105626 x = -5.123105626 Simplifying x = -5.123105626

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.123105626, -5.123105626}

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