5x^2-42x+8=0

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Solution for 5x^2-42x+8=0 equation:


Simplifying
5x2 + -42x + 8 = 0

Reorder the terms:
8 + -42x + 5x2 = 0

Solving
8 + -42x + 5x2 = 0

Solving for variable 'x'.

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

Divide each side by '5'.
1.6 + -8.4x + x2 = 0

Move the constant term to the right:

Add '-1.6' to each side of the equation.
1.6 + -8.4x + -1.6 + x2 = 0 + -1.6

Reorder the terms:
1.6 + -1.6 + -8.4x + x2 = 0 + -1.6

Combine like terms: 1.6 + -1.6 = 0.0
0.0 + -8.4x + x2 = 0 + -1.6
-8.4x + x2 = 0 + -1.6

Combine like terms: 0 + -1.6 = -1.6
-8.4x + x2 = -1.6

The x term is -8.4x.  Take half its coefficient (-4.2).
Square it (17.64) and add it to both sides.

Add '17.64' to each side of the equation.
-8.4x + 17.64 + x2 = -1.6 + 17.64

Reorder the terms:
17.64 + -8.4x + x2 = -1.6 + 17.64

Combine like terms: -1.6 + 17.64 = 16.04
17.64 + -8.4x + x2 = 16.04

Factor a perfect square on the left side:
(x + -4.2)(x + -4.2) = 16.04

Calculate the square root of the right side: 4.004996879

Break this problem into two subproblems by setting 
(x + -4.2) equal to 4.004996879 and -4.004996879.

Subproblem 1

x + -4.2 = 4.004996879 Simplifying x + -4.2 = 4.004996879 Reorder the terms: -4.2 + x = 4.004996879 Solving -4.2 + x = 4.004996879 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '4.2' to each side of the equation. -4.2 + 4.2 + x = 4.004996879 + 4.2 Combine like terms: -4.2 + 4.2 = 0.0 0.0 + x = 4.004996879 + 4.2 x = 4.004996879 + 4.2 Combine like terms: 4.004996879 + 4.2 = 8.204996879 x = 8.204996879 Simplifying x = 8.204996879

Subproblem 2

x + -4.2 = -4.004996879 Simplifying x + -4.2 = -4.004996879 Reorder the terms: -4.2 + x = -4.004996879 Solving -4.2 + x = -4.004996879 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '4.2' to each side of the equation. -4.2 + 4.2 + x = -4.004996879 + 4.2 Combine like terms: -4.2 + 4.2 = 0.0 0.0 + x = -4.004996879 + 4.2 x = -4.004996879 + 4.2 Combine like terms: -4.004996879 + 4.2 = 0.195003121 x = 0.195003121 Simplifying x = 0.195003121

Solution

The solution to the problem is based on the solutions from the subproblems. x = {8.204996879, 0.195003121}

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