100=-.4x^2+57x-13

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Solution for 100=-.4x^2+57x-13 equation:


Simplifying
100 = -0.4x2 + 57x + -13

Reorder the terms:
100 = -13 + 57x + -0.4x2

Solving
100 = -13 + 57x + -0.4x2

Solving for variable 'x'.

Combine like terms: 100 + 13 = 113
113 + -57x + 0.4x2 = -13 + 57x + -0.4x2 + 13 + -57x + 0.4x2

Reorder the terms:
113 + -57x + 0.4x2 = -13 + 13 + 57x + -57x + -0.4x2 + 0.4x2

Combine like terms: -13 + 13 = 0
113 + -57x + 0.4x2 = 0 + 57x + -57x + -0.4x2 + 0.4x2
113 + -57x + 0.4x2 = 57x + -57x + -0.4x2 + 0.4x2

Combine like terms: 57x + -57x = 0
113 + -57x + 0.4x2 = 0 + -0.4x2 + 0.4x2
113 + -57x + 0.4x2 = -0.4x2 + 0.4x2

Combine like terms: -0.4x2 + 0.4x2 = 0.0
113 + -57x + 0.4x2 = 0.0

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

Divide each side by '0.4'.
282.5 + -142.5x + x2 = 0

Move the constant term to the right:

Add '-282.5' to each side of the equation.
282.5 + -142.5x + -282.5 + x2 = 0 + -282.5

Reorder the terms:
282.5 + -282.5 + -142.5x + x2 = 0 + -282.5

Combine like terms: 282.5 + -282.5 = 0.0
0.0 + -142.5x + x2 = 0 + -282.5
-142.5x + x2 = 0 + -282.5

Combine like terms: 0 + -282.5 = -282.5
-142.5x + x2 = -282.5

The x term is -142.5x.  Take half its coefficient (-71.25).
Square it (5076.5625) and add it to both sides.

Add '5076.5625' to each side of the equation.
-142.5x + 5076.5625 + x2 = -282.5 + 5076.5625

Reorder the terms:
5076.5625 + -142.5x + x2 = -282.5 + 5076.5625

Combine like terms: -282.5 + 5076.5625 = 4794.0625
5076.5625 + -142.5x + x2 = 4794.0625

Factor a perfect square on the left side:
(x + -71.25)(x + -71.25) = 4794.0625

Calculate the square root of the right side: 69.239168828

Break this problem into two subproblems by setting 
(x + -71.25) equal to 69.239168828 and -69.239168828.

Subproblem 1

x + -71.25 = 69.239168828 Simplifying x + -71.25 = 69.239168828 Reorder the terms: -71.25 + x = 69.239168828 Solving -71.25 + x = 69.239168828 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '71.25' to each side of the equation. -71.25 + 71.25 + x = 69.239168828 + 71.25 Combine like terms: -71.25 + 71.25 = 0.00 0.00 + x = 69.239168828 + 71.25 x = 69.239168828 + 71.25 Combine like terms: 69.239168828 + 71.25 = 140.489168828 x = 140.489168828 Simplifying x = 140.489168828

Subproblem 2

x + -71.25 = -69.239168828 Simplifying x + -71.25 = -69.239168828 Reorder the terms: -71.25 + x = -69.239168828 Solving -71.25 + x = -69.239168828 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '71.25' to each side of the equation. -71.25 + 71.25 + x = -69.239168828 + 71.25 Combine like terms: -71.25 + 71.25 = 0.00 0.00 + x = -69.239168828 + 71.25 x = -69.239168828 + 71.25 Combine like terms: -69.239168828 + 71.25 = 2.010831172 x = 2.010831172 Simplifying x = 2.010831172

Solution

The solution to the problem is based on the solutions from the subproblems. x = {140.489168828, 2.010831172}

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