400x^2+4x-9=0

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Solution for 400x^2+4x-9=0 equation:


Simplifying
400x2 + 4x + -9 = 0

Reorder the terms:
-9 + 4x + 400x2 = 0

Solving
-9 + 4x + 400x2 = 0

Solving for variable 'x'.

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

Divide each side by '400'.
-0.0225 + 0.01x + x2 = 0

Move the constant term to the right:

Add '0.0225' to each side of the equation.
-0.0225 + 0.01x + 0.0225 + x2 = 0 + 0.0225

Reorder the terms:
-0.0225 + 0.0225 + 0.01x + x2 = 0 + 0.0225

Combine like terms: -0.0225 + 0.0225 = 0.0000
0.0000 + 0.01x + x2 = 0 + 0.0225
0.01x + x2 = 0 + 0.0225

Combine like terms: 0 + 0.0225 = 0.0225
0.01x + x2 = 0.0225

The x term is 0.01x.  Take half its coefficient (0.005).
Square it (0.000025) and add it to both sides.

Add '0.000025' to each side of the equation.
0.01x + 0.000025 + x2 = 0.0225 + 0.000025

Reorder the terms:
0.000025 + 0.01x + x2 = 0.0225 + 0.000025

Combine like terms: 0.0225 + 0.000025 = 0.022525
0.000025 + 0.01x + x2 = 0.022525

Factor a perfect square on the left side:
(x + 0.005)(x + 0.005) = 0.022525

Calculate the square root of the right side: 0.15008331

Break this problem into two subproblems by setting 
(x + 0.005) equal to 0.15008331 and -0.15008331.

Subproblem 1

x + 0.005 = 0.15008331 Simplifying x + 0.005 = 0.15008331 Reorder the terms: 0.005 + x = 0.15008331 Solving 0.005 + x = 0.15008331 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.005' to each side of the equation. 0.005 + -0.005 + x = 0.15008331 + -0.005 Combine like terms: 0.005 + -0.005 = 0.000 0.000 + x = 0.15008331 + -0.005 x = 0.15008331 + -0.005 Combine like terms: 0.15008331 + -0.005 = 0.14508331 x = 0.14508331 Simplifying x = 0.14508331

Subproblem 2

x + 0.005 = -0.15008331 Simplifying x + 0.005 = -0.15008331 Reorder the terms: 0.005 + x = -0.15008331 Solving 0.005 + x = -0.15008331 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.005' to each side of the equation. 0.005 + -0.005 + x = -0.15008331 + -0.005 Combine like terms: 0.005 + -0.005 = 0.000 0.000 + x = -0.15008331 + -0.005 x = -0.15008331 + -0.005 Combine like terms: -0.15008331 + -0.005 = -0.15508331 x = -0.15508331 Simplifying x = -0.15508331

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.14508331, -0.15508331}

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