x^2+42x-9=0

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Solution for x^2+42x-9=0 equation:


Simplifying
x2 + 42x + -9 = 0

Reorder the terms:
-9 + 42x + x2 = 0

Solving
-9 + 42x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '9' to each side of the equation.
-9 + 42x + 9 + x2 = 0 + 9

Reorder the terms:
-9 + 9 + 42x + x2 = 0 + 9

Combine like terms: -9 + 9 = 0
0 + 42x + x2 = 0 + 9
42x + x2 = 0 + 9

Combine like terms: 0 + 9 = 9
42x + x2 = 9

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 = 9 + 441

Reorder the terms:
441 + 42x + x2 = 9 + 441

Combine like terms: 9 + 441 = 450
441 + 42x + x2 = 450

Factor a perfect square on the left side:
(x + 21)(x + 21) = 450

Calculate the square root of the right side: 21.213203436

Break this problem into two subproblems by setting 
(x + 21) equal to 21.213203436 and -21.213203436.

Subproblem 1

x + 21 = 21.213203436 Simplifying x + 21 = 21.213203436 Reorder the terms: 21 + x = 21.213203436 Solving 21 + x = 21.213203436 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 = 21.213203436 + -21 Combine like terms: 21 + -21 = 0 0 + x = 21.213203436 + -21 x = 21.213203436 + -21 Combine like terms: 21.213203436 + -21 = 0.213203436 x = 0.213203436 Simplifying x = 0.213203436

Subproblem 2

x + 21 = -21.213203436 Simplifying x + 21 = -21.213203436 Reorder the terms: 21 + x = -21.213203436 Solving 21 + x = -21.213203436 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 = -21.213203436 + -21 Combine like terms: 21 + -21 = 0 0 + x = -21.213203436 + -21 x = -21.213203436 + -21 Combine like terms: -21.213203436 + -21 = -42.213203436 x = -42.213203436 Simplifying x = -42.213203436

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.213203436, -42.213203436}

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