x^2+42x-396=0

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Solution for x^2+42x-396=0 equation:


Simplifying
x2 + 42x + -396 = 0

Reorder the terms:
-396 + 42x + x2 = 0

Solving
-396 + 42x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '396' to each side of the equation.
-396 + 42x + 396 + x2 = 0 + 396

Reorder the terms:
-396 + 396 + 42x + x2 = 0 + 396

Combine like terms: -396 + 396 = 0
0 + 42x + x2 = 0 + 396
42x + x2 = 0 + 396

Combine like terms: 0 + 396 = 396
42x + x2 = 396

The x term is 42x.  Take half its coefficient (21).
Square it (441) and add it to both sides.

Add '441' to each side of the equation.
42x + 441 + x2 = 396 + 441

Reorder the terms:
441 + 42x + x2 = 396 + 441

Combine like terms: 396 + 441 = 837
441 + 42x + x2 = 837

Factor a perfect square on the left side:
(x + 21)(x + 21) = 837

Calculate the square root of the right side: 28.930952283

Break this problem into two subproblems by setting 
(x + 21) equal to 28.930952283 and -28.930952283.

Subproblem 1

x + 21 = 28.930952283 Simplifying x + 21 = 28.930952283 Reorder the terms: 21 + x = 28.930952283 Solving 21 + x = 28.930952283 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-21' to each side of the equation. 21 + -21 + x = 28.930952283 + -21 Combine like terms: 21 + -21 = 0 0 + x = 28.930952283 + -21 x = 28.930952283 + -21 Combine like terms: 28.930952283 + -21 = 7.930952283 x = 7.930952283 Simplifying x = 7.930952283

Subproblem 2

x + 21 = -28.930952283 Simplifying x + 21 = -28.930952283 Reorder the terms: 21 + x = -28.930952283 Solving 21 + x = -28.930952283 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-21' to each side of the equation. 21 + -21 + x = -28.930952283 + -21 Combine like terms: 21 + -21 = 0 0 + x = -28.930952283 + -21 x = -28.930952283 + -21 Combine like terms: -28.930952283 + -21 = -49.930952283 x = -49.930952283 Simplifying x = -49.930952283

Solution

The solution to the problem is based on the solutions from the subproblems. x = {7.930952283, -49.930952283}

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