x=-5x^2+790x-400

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Solution for x=-5x^2+790x-400 equation:


Simplifying
x = -5x2 + 790x + -400

Reorder the terms:
x = -400 + 790x + -5x2

Solving
x = -400 + 790x + -5x2

Solving for variable 'x'.

Reorder the terms:
400 + x + -790x + 5x2 = -400 + 790x + -5x2 + 400 + -790x + 5x2

Combine like terms: x + -790x = -789x
400 + -789x + 5x2 = -400 + 790x + -5x2 + 400 + -790x + 5x2

Reorder the terms:
400 + -789x + 5x2 = -400 + 400 + 790x + -790x + -5x2 + 5x2

Combine like terms: -400 + 400 = 0
400 + -789x + 5x2 = 0 + 790x + -790x + -5x2 + 5x2
400 + -789x + 5x2 = 790x + -790x + -5x2 + 5x2

Combine like terms: 790x + -790x = 0
400 + -789x + 5x2 = 0 + -5x2 + 5x2
400 + -789x + 5x2 = -5x2 + 5x2

Combine like terms: -5x2 + 5x2 = 0
400 + -789x + 5x2 = 0

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

Divide each side by '5'.
80 + -157.8x + x2 = 0

Move the constant term to the right:

Add '-80' to each side of the equation.
80 + -157.8x + -80 + x2 = 0 + -80

Reorder the terms:
80 + -80 + -157.8x + x2 = 0 + -80

Combine like terms: 80 + -80 = 0
0 + -157.8x + x2 = 0 + -80
-157.8x + x2 = 0 + -80

Combine like terms: 0 + -80 = -80
-157.8x + x2 = -80

The x term is -157.8x.  Take half its coefficient (-78.9).
Square it (6225.21) and add it to both sides.

Add '6225.21' to each side of the equation.
-157.8x + 6225.21 + x2 = -80 + 6225.21

Reorder the terms:
6225.21 + -157.8x + x2 = -80 + 6225.21

Combine like terms: -80 + 6225.21 = 6145.21
6225.21 + -157.8x + x2 = 6145.21

Factor a perfect square on the left side:
(x + -78.9)(x + -78.9) = 6145.21

Calculate the square root of the right side: 78.391389833

Break this problem into two subproblems by setting 
(x + -78.9) equal to 78.391389833 and -78.391389833.

Subproblem 1

x + -78.9 = 78.391389833 Simplifying x + -78.9 = 78.391389833 Reorder the terms: -78.9 + x = 78.391389833 Solving -78.9 + x = 78.391389833 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '78.9' to each side of the equation. -78.9 + 78.9 + x = 78.391389833 + 78.9 Combine like terms: -78.9 + 78.9 = 0.0 0.0 + x = 78.391389833 + 78.9 x = 78.391389833 + 78.9 Combine like terms: 78.391389833 + 78.9 = 157.291389833 x = 157.291389833 Simplifying x = 157.291389833

Subproblem 2

x + -78.9 = -78.391389833 Simplifying x + -78.9 = -78.391389833 Reorder the terms: -78.9 + x = -78.391389833 Solving -78.9 + x = -78.391389833 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '78.9' to each side of the equation. -78.9 + 78.9 + x = -78.391389833 + 78.9 Combine like terms: -78.9 + 78.9 = 0.0 0.0 + x = -78.391389833 + 78.9 x = -78.391389833 + 78.9 Combine like terms: -78.391389833 + 78.9 = 0.508610167 x = 0.508610167 Simplifying x = 0.508610167

Solution

The solution to the problem is based on the solutions from the subproblems. x = {157.291389833, 0.508610167}

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