5x^2-42x-4=0

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Solution for 5x^2-42x-4=0 equation:


Simplifying
5x2 + -42x + -4 = 0

Reorder the terms:
-4 + -42x + 5x2 = 0

Solving
-4 + -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'.
-0.8 + -8.4x + x2 = 0

Move the constant term to the right:

Add '0.8' to each side of the equation.
-0.8 + -8.4x + 0.8 + x2 = 0 + 0.8

Reorder the terms:
-0.8 + 0.8 + -8.4x + x2 = 0 + 0.8

Combine like terms: -0.8 + 0.8 = 0.0
0.0 + -8.4x + x2 = 0 + 0.8
-8.4x + x2 = 0 + 0.8

Combine like terms: 0 + 0.8 = 0.8
-8.4x + x2 = 0.8

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 = 0.8 + 17.64

Reorder the terms:
17.64 + -8.4x + x2 = 0.8 + 17.64

Combine like terms: 0.8 + 17.64 = 18.44
17.64 + -8.4x + x2 = 18.44

Factor a perfect square on the left side:
(x + -4.2)(x + -4.2) = 18.44

Calculate the square root of the right side: 4.294182111

Break this problem into two subproblems by setting 
(x + -4.2) equal to 4.294182111 and -4.294182111.

Subproblem 1

x + -4.2 = 4.294182111 Simplifying x + -4.2 = 4.294182111 Reorder the terms: -4.2 + x = 4.294182111 Solving -4.2 + x = 4.294182111 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 = 4.294182111 + 4.2 Combine like terms: -4.2 + 4.2 = 0.0 0.0 + x = 4.294182111 + 4.2 x = 4.294182111 + 4.2 Combine like terms: 4.294182111 + 4.2 = 8.494182111 x = 8.494182111 Simplifying x = 8.494182111

Subproblem 2

x + -4.2 = -4.294182111 Simplifying x + -4.2 = -4.294182111 Reorder the terms: -4.2 + x = -4.294182111 Solving -4.2 + x = -4.294182111 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 = -4.294182111 + 4.2 Combine like terms: -4.2 + 4.2 = 0.0 0.0 + x = -4.294182111 + 4.2 x = -4.294182111 + 4.2 Combine like terms: -4.294182111 + 4.2 = -0.094182111 x = -0.094182111 Simplifying x = -0.094182111

Solution

The solution to the problem is based on the solutions from the subproblems. x = {8.494182111, -0.094182111}

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