4x^2-5x-400=0

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Solution for 4x^2-5x-400=0 equation:


Simplifying
4x2 + -5x + -400 = 0

Reorder the terms:
-400 + -5x + 4x2 = 0

Solving
-400 + -5x + 4x2 = 0

Solving for variable 'x'.

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

Divide each side by '4'.
-100 + -1.25x + x2 = 0

Move the constant term to the right:

Add '100' to each side of the equation.
-100 + -1.25x + 100 + x2 = 0 + 100

Reorder the terms:
-100 + 100 + -1.25x + x2 = 0 + 100

Combine like terms: -100 + 100 = 0
0 + -1.25x + x2 = 0 + 100
-1.25x + x2 = 0 + 100

Combine like terms: 0 + 100 = 100
-1.25x + x2 = 100

The x term is -1.25x.  Take half its coefficient (-0.625).
Square it (0.390625) and add it to both sides.

Add '0.390625' to each side of the equation.
-1.25x + 0.390625 + x2 = 100 + 0.390625

Reorder the terms:
0.390625 + -1.25x + x2 = 100 + 0.390625

Combine like terms: 100 + 0.390625 = 100.390625
0.390625 + -1.25x + x2 = 100.390625

Factor a perfect square on the left side:
(x + -0.625)(x + -0.625) = 100.390625

Calculate the square root of the right side: 10.019512214

Break this problem into two subproblems by setting 
(x + -0.625) equal to 10.019512214 and -10.019512214.

Subproblem 1

x + -0.625 = 10.019512214 Simplifying x + -0.625 = 10.019512214 Reorder the terms: -0.625 + x = 10.019512214 Solving -0.625 + x = 10.019512214 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.625' to each side of the equation. -0.625 + 0.625 + x = 10.019512214 + 0.625 Combine like terms: -0.625 + 0.625 = 0.000 0.000 + x = 10.019512214 + 0.625 x = 10.019512214 + 0.625 Combine like terms: 10.019512214 + 0.625 = 10.644512214 x = 10.644512214 Simplifying x = 10.644512214

Subproblem 2

x + -0.625 = -10.019512214 Simplifying x + -0.625 = -10.019512214 Reorder the terms: -0.625 + x = -10.019512214 Solving -0.625 + x = -10.019512214 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.625' to each side of the equation. -0.625 + 0.625 + x = -10.019512214 + 0.625 Combine like terms: -0.625 + 0.625 = 0.000 0.000 + x = -10.019512214 + 0.625 x = -10.019512214 + 0.625 Combine like terms: -10.019512214 + 0.625 = -9.394512214 x = -9.394512214 Simplifying x = -9.394512214

Solution

The solution to the problem is based on the solutions from the subproblems. x = {10.644512214, -9.394512214}

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