x^2+2x-1=18

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Solution for x^2+2x-1=18 equation:


Simplifying
x2 + 2x + -1 = 18

Reorder the terms:
-1 + 2x + x2 = 18

Solving
-1 + 2x + x2 = 18

Solving for variable 'x'.

Reorder the terms:
-1 + -18 + 2x + x2 = 18 + -18

Combine like terms: -1 + -18 = -19
-19 + 2x + x2 = 18 + -18

Combine like terms: 18 + -18 = 0
-19 + 2x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '19' to each side of the equation.
-19 + 2x + 19 + x2 = 0 + 19

Reorder the terms:
-19 + 19 + 2x + x2 = 0 + 19

Combine like terms: -19 + 19 = 0
0 + 2x + x2 = 0 + 19
2x + x2 = 0 + 19

Combine like terms: 0 + 19 = 19
2x + x2 = 19

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 = 19 + 1

Reorder the terms:
1 + 2x + x2 = 19 + 1

Combine like terms: 19 + 1 = 20
1 + 2x + x2 = 20

Factor a perfect square on the left side:
(x + 1)(x + 1) = 20

Calculate the square root of the right side: 4.472135955

Break this problem into two subproblems by setting 
(x + 1) equal to 4.472135955 and -4.472135955.

Subproblem 1

x + 1 = 4.472135955 Simplifying x + 1 = 4.472135955 Reorder the terms: 1 + x = 4.472135955 Solving 1 + x = 4.472135955 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 = 4.472135955 + -1 Combine like terms: 1 + -1 = 0 0 + x = 4.472135955 + -1 x = 4.472135955 + -1 Combine like terms: 4.472135955 + -1 = 3.472135955 x = 3.472135955 Simplifying x = 3.472135955

Subproblem 2

x + 1 = -4.472135955 Simplifying x + 1 = -4.472135955 Reorder the terms: 1 + x = -4.472135955 Solving 1 + x = -4.472135955 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 = -4.472135955 + -1 Combine like terms: 1 + -1 = 0 0 + x = -4.472135955 + -1 x = -4.472135955 + -1 Combine like terms: -4.472135955 + -1 = -5.472135955 x = -5.472135955 Simplifying x = -5.472135955

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.472135955, -5.472135955}

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