2x^2-9x=400

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Solution for 2x^2-9x=400 equation:


Simplifying
2x2 + -9x = 400

Reorder the terms:
-9x + 2x2 = 400

Solving
-9x + 2x2 = 400

Solving for variable 'x'.

Reorder the terms:
-400 + -9x + 2x2 = 400 + -400

Combine like terms: 400 + -400 = 0
-400 + -9x + 2x2 = 0

Begin completing the square.  Divide all terms by
2 the coefficient of the squared term: 

Divide each side by '2'.
-200 + -4.5x + x2 = 0

Move the constant term to the right:

Add '200' to each side of the equation.
-200 + -4.5x + 200 + x2 = 0 + 200

Reorder the terms:
-200 + 200 + -4.5x + x2 = 0 + 200

Combine like terms: -200 + 200 = 0
0 + -4.5x + x2 = 0 + 200
-4.5x + x2 = 0 + 200

Combine like terms: 0 + 200 = 200
-4.5x + x2 = 200

The x term is -4.5x.  Take half its coefficient (-2.25).
Square it (5.0625) and add it to both sides.

Add '5.0625' to each side of the equation.
-4.5x + 5.0625 + x2 = 200 + 5.0625

Reorder the terms:
5.0625 + -4.5x + x2 = 200 + 5.0625

Combine like terms: 200 + 5.0625 = 205.0625
5.0625 + -4.5x + x2 = 205.0625

Factor a perfect square on the left side:
(x + -2.25)(x + -2.25) = 205.0625

Calculate the square root of the right side: 14.320003492

Break this problem into two subproblems by setting 
(x + -2.25) equal to 14.320003492 and -14.320003492.

Subproblem 1

x + -2.25 = 14.320003492 Simplifying x + -2.25 = 14.320003492 Reorder the terms: -2.25 + x = 14.320003492 Solving -2.25 + x = 14.320003492 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2.25' to each side of the equation. -2.25 + 2.25 + x = 14.320003492 + 2.25 Combine like terms: -2.25 + 2.25 = 0.00 0.00 + x = 14.320003492 + 2.25 x = 14.320003492 + 2.25 Combine like terms: 14.320003492 + 2.25 = 16.570003492 x = 16.570003492 Simplifying x = 16.570003492

Subproblem 2

x + -2.25 = -14.320003492 Simplifying x + -2.25 = -14.320003492 Reorder the terms: -2.25 + x = -14.320003492 Solving -2.25 + x = -14.320003492 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2.25' to each side of the equation. -2.25 + 2.25 + x = -14.320003492 + 2.25 Combine like terms: -2.25 + 2.25 = 0.00 0.00 + x = -14.320003492 + 2.25 x = -14.320003492 + 2.25 Combine like terms: -14.320003492 + 2.25 = -12.070003492 x = -12.070003492 Simplifying x = -12.070003492

Solution

The solution to the problem is based on the solutions from the subproblems. x = {16.570003492, -12.070003492}

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