x^2+9x-42=0

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


Simplifying
x2 + 9x + -42 = 0

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

Solving
-42 + 9x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

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

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

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

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

The x term is 9x.  Take half its coefficient (4.5).
Square it (20.25) and add it to both sides.

Add '20.25' to each side of the equation.
9x + 20.25 + x2 = 42 + 20.25

Reorder the terms:
20.25 + 9x + x2 = 42 + 20.25

Combine like terms: 42 + 20.25 = 62.25
20.25 + 9x + x2 = 62.25

Factor a perfect square on the left side:
(x + 4.5)(x + 4.5) = 62.25

Calculate the square root of the right side: 7.889866919

Break this problem into two subproblems by setting 
(x + 4.5) equal to 7.889866919 and -7.889866919.

Subproblem 1

x + 4.5 = 7.889866919 Simplifying x + 4.5 = 7.889866919 Reorder the terms: 4.5 + x = 7.889866919 Solving 4.5 + x = 7.889866919 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-4.5' to each side of the equation. 4.5 + -4.5 + x = 7.889866919 + -4.5 Combine like terms: 4.5 + -4.5 = 0.0 0.0 + x = 7.889866919 + -4.5 x = 7.889866919 + -4.5 Combine like terms: 7.889866919 + -4.5 = 3.389866919 x = 3.389866919 Simplifying x = 3.389866919

Subproblem 2

x + 4.5 = -7.889866919 Simplifying x + 4.5 = -7.889866919 Reorder the terms: 4.5 + x = -7.889866919 Solving 4.5 + x = -7.889866919 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-4.5' to each side of the equation. 4.5 + -4.5 + x = -7.889866919 + -4.5 Combine like terms: 4.5 + -4.5 = 0.0 0.0 + x = -7.889866919 + -4.5 x = -7.889866919 + -4.5 Combine like terms: -7.889866919 + -4.5 = -12.389866919 x = -12.389866919 Simplifying x = -12.389866919

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.389866919, -12.389866919}

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