x^2-42x-216=0

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Solution for x^2-42x-216=0 equation:


Simplifying
x2 + -42x + -216 = 0

Reorder the terms:
-216 + -42x + x2 = 0

Solving
-216 + -42x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '216' to each side of the equation.
-216 + -42x + 216 + x2 = 0 + 216

Reorder the terms:
-216 + 216 + -42x + x2 = 0 + 216

Combine like terms: -216 + 216 = 0
0 + -42x + x2 = 0 + 216
-42x + x2 = 0 + 216

Combine like terms: 0 + 216 = 216
-42x + x2 = 216

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 = 216 + 441

Reorder the terms:
441 + -42x + x2 = 216 + 441

Combine like terms: 216 + 441 = 657
441 + -42x + x2 = 657

Factor a perfect square on the left side:
(x + -21)(x + -21) = 657

Calculate the square root of the right side: 25.632011236

Break this problem into two subproblems by setting 
(x + -21) equal to 25.632011236 and -25.632011236.

Subproblem 1

x + -21 = 25.632011236 Simplifying x + -21 = 25.632011236 Reorder the terms: -21 + x = 25.632011236 Solving -21 + x = 25.632011236 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 = 25.632011236 + 21 Combine like terms: -21 + 21 = 0 0 + x = 25.632011236 + 21 x = 25.632011236 + 21 Combine like terms: 25.632011236 + 21 = 46.632011236 x = 46.632011236 Simplifying x = 46.632011236

Subproblem 2

x + -21 = -25.632011236 Simplifying x + -21 = -25.632011236 Reorder the terms: -21 + x = -25.632011236 Solving -21 + x = -25.632011236 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 = -25.632011236 + 21 Combine like terms: -21 + 21 = 0 0 + x = -25.632011236 + 21 x = -25.632011236 + 21 Combine like terms: -25.632011236 + 21 = -4.632011236 x = -4.632011236 Simplifying x = -4.632011236

Solution

The solution to the problem is based on the solutions from the subproblems. x = {46.632011236, -4.632011236}

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