8x^2-34x-21=0

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Solution for 8x^2-34x-21=0 equation:


Simplifying
8x2 + -34x + -21 = 0

Reorder the terms:
-21 + -34x + 8x2 = 0

Solving
-21 + -34x + 8x2 = 0

Solving for variable 'x'.

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

Divide each side by '8'.
-2.625 + -4.25x + x2 = 0

Move the constant term to the right:

Add '2.625' to each side of the equation.
-2.625 + -4.25x + 2.625 + x2 = 0 + 2.625

Reorder the terms:
-2.625 + 2.625 + -4.25x + x2 = 0 + 2.625

Combine like terms: -2.625 + 2.625 = 0.000
0.000 + -4.25x + x2 = 0 + 2.625
-4.25x + x2 = 0 + 2.625

Combine like terms: 0 + 2.625 = 2.625
-4.25x + x2 = 2.625

The x term is -4.25x.  Take half its coefficient (-2.125).
Square it (4.515625) and add it to both sides.

Add '4.515625' to each side of the equation.
-4.25x + 4.515625 + x2 = 2.625 + 4.515625

Reorder the terms:
4.515625 + -4.25x + x2 = 2.625 + 4.515625

Combine like terms: 2.625 + 4.515625 = 7.140625
4.515625 + -4.25x + x2 = 7.140625

Factor a perfect square on the left side:
(x + -2.125)(x + -2.125) = 7.140625

Calculate the square root of the right side: 2.672194791

Break this problem into two subproblems by setting 
(x + -2.125) equal to 2.672194791 and -2.672194791.

Subproblem 1

x + -2.125 = 2.672194791 Simplifying x + -2.125 = 2.672194791 Reorder the terms: -2.125 + x = 2.672194791 Solving -2.125 + x = 2.672194791 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2.125' to each side of the equation. -2.125 + 2.125 + x = 2.672194791 + 2.125 Combine like terms: -2.125 + 2.125 = 0.000 0.000 + x = 2.672194791 + 2.125 x = 2.672194791 + 2.125 Combine like terms: 2.672194791 + 2.125 = 4.797194791 x = 4.797194791 Simplifying x = 4.797194791

Subproblem 2

x + -2.125 = -2.672194791 Simplifying x + -2.125 = -2.672194791 Reorder the terms: -2.125 + x = -2.672194791 Solving -2.125 + x = -2.672194791 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2.125' to each side of the equation. -2.125 + 2.125 + x = -2.672194791 + 2.125 Combine like terms: -2.125 + 2.125 = 0.000 0.000 + x = -2.672194791 + 2.125 x = -2.672194791 + 2.125 Combine like terms: -2.672194791 + 2.125 = -0.547194791 x = -0.547194791 Simplifying x = -0.547194791

Solution

The solution to the problem is based on the solutions from the subproblems. x = {4.797194791, -0.547194791}

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