x^2+2x=390

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Solution for x^2+2x=390 equation:


Simplifying
x2 + 2x = 390

Reorder the terms:
2x + x2 = 390

Solving
2x + x2 = 390

Solving for variable 'x'.

Reorder the terms:
-390 + 2x + x2 = 390 + -390

Combine like terms: 390 + -390 = 0
-390 + 2x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '390' to each side of the equation.
-390 + 2x + 390 + x2 = 0 + 390

Reorder the terms:
-390 + 390 + 2x + x2 = 0 + 390

Combine like terms: -390 + 390 = 0
0 + 2x + x2 = 0 + 390
2x + x2 = 0 + 390

Combine like terms: 0 + 390 = 390
2x + x2 = 390

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 = 390 + 1

Reorder the terms:
1 + 2x + x2 = 390 + 1

Combine like terms: 390 + 1 = 391
1 + 2x + x2 = 391

Factor a perfect square on the left side:
(x + 1)(x + 1) = 391

Calculate the square root of the right side: 19.773719933

Break this problem into two subproblems by setting 
(x + 1) equal to 19.773719933 and -19.773719933.

Subproblem 1

x + 1 = 19.773719933 Simplifying x + 1 = 19.773719933 Reorder the terms: 1 + x = 19.773719933 Solving 1 + x = 19.773719933 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 = 19.773719933 + -1 Combine like terms: 1 + -1 = 0 0 + x = 19.773719933 + -1 x = 19.773719933 + -1 Combine like terms: 19.773719933 + -1 = 18.773719933 x = 18.773719933 Simplifying x = 18.773719933

Subproblem 2

x + 1 = -19.773719933 Simplifying x + 1 = -19.773719933 Reorder the terms: 1 + x = -19.773719933 Solving 1 + x = -19.773719933 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 = -19.773719933 + -1 Combine like terms: 1 + -1 = 0 0 + x = -19.773719933 + -1 x = -19.773719933 + -1 Combine like terms: -19.773719933 + -1 = -20.773719933 x = -20.773719933 Simplifying x = -20.773719933

Solution

The solution to the problem is based on the solutions from the subproblems. x = {18.773719933, -20.773719933}

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