x^2+9x=640

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Solution for x^2+9x=640 equation:


Simplifying
x2 + 9x = 640

Reorder the terms:
9x + x2 = 640

Solving
9x + x2 = 640

Solving for variable 'x'.

Reorder the terms:
-640 + 9x + x2 = 640 + -640

Combine like terms: 640 + -640 = 0
-640 + 9x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '640' to each side of the equation.
-640 + 9x + 640 + x2 = 0 + 640

Reorder the terms:
-640 + 640 + 9x + x2 = 0 + 640

Combine like terms: -640 + 640 = 0
0 + 9x + x2 = 0 + 640
9x + x2 = 0 + 640

Combine like terms: 0 + 640 = 640
9x + x2 = 640

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 = 640 + 20.25

Reorder the terms:
20.25 + 9x + x2 = 640 + 20.25

Combine like terms: 640 + 20.25 = 660.25
20.25 + 9x + x2 = 660.25

Factor a perfect square on the left side:
(x + 4.5)(x + 4.5) = 660.25

Calculate the square root of the right side: 25.695330315

Break this problem into two subproblems by setting 
(x + 4.5) equal to 25.695330315 and -25.695330315.

Subproblem 1

x + 4.5 = 25.695330315 Simplifying x + 4.5 = 25.695330315 Reorder the terms: 4.5 + x = 25.695330315 Solving 4.5 + x = 25.695330315 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 = 25.695330315 + -4.5 Combine like terms: 4.5 + -4.5 = 0.0 0.0 + x = 25.695330315 + -4.5 x = 25.695330315 + -4.5 Combine like terms: 25.695330315 + -4.5 = 21.195330315 x = 21.195330315 Simplifying x = 21.195330315

Subproblem 2

x + 4.5 = -25.695330315 Simplifying x + 4.5 = -25.695330315 Reorder the terms: 4.5 + x = -25.695330315 Solving 4.5 + x = -25.695330315 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 = -25.695330315 + -4.5 Combine like terms: 4.5 + -4.5 = 0.0 0.0 + x = -25.695330315 + -4.5 x = -25.695330315 + -4.5 Combine like terms: -25.695330315 + -4.5 = -30.195330315 x = -30.195330315 Simplifying x = -30.195330315

Solution

The solution to the problem is based on the solutions from the subproblems. x = {21.195330315, -30.195330315}

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