6x^2-21x+8=0

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Solution for 6x^2-21x+8=0 equation:


Simplifying
6x2 + -21x + 8 = 0

Reorder the terms:
8 + -21x + 6x2 = 0

Solving
8 + -21x + 6x2 = 0

Solving for variable 'x'.

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

Divide each side by '6'.
1.333333333 + -3.5x + x2 = 0

Move the constant term to the right:

Add '-1.333333333' to each side of the equation.
1.333333333 + -3.5x + -1.333333333 + x2 = 0 + -1.333333333

Reorder the terms:
1.333333333 + -1.333333333 + -3.5x + x2 = 0 + -1.333333333

Combine like terms: 1.333333333 + -1.333333333 = 0.000000000
0.000000000 + -3.5x + x2 = 0 + -1.333333333
-3.5x + x2 = 0 + -1.333333333

Combine like terms: 0 + -1.333333333 = -1.333333333
-3.5x + x2 = -1.333333333

The x term is -3.5x.  Take half its coefficient (-1.75).
Square it (3.0625) and add it to both sides.

Add '3.0625' to each side of the equation.
-3.5x + 3.0625 + x2 = -1.333333333 + 3.0625

Reorder the terms:
3.0625 + -3.5x + x2 = -1.333333333 + 3.0625

Combine like terms: -1.333333333 + 3.0625 = 1.729166667
3.0625 + -3.5x + x2 = 1.729166667

Factor a perfect square on the left side:
(x + -1.75)(x + -1.75) = 1.729166667

Calculate the square root of the right side: 1.31497782

Break this problem into two subproblems by setting 
(x + -1.75) equal to 1.31497782 and -1.31497782.

Subproblem 1

x + -1.75 = 1.31497782 Simplifying x + -1.75 = 1.31497782 Reorder the terms: -1.75 + x = 1.31497782 Solving -1.75 + x = 1.31497782 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.75' to each side of the equation. -1.75 + 1.75 + x = 1.31497782 + 1.75 Combine like terms: -1.75 + 1.75 = 0.00 0.00 + x = 1.31497782 + 1.75 x = 1.31497782 + 1.75 Combine like terms: 1.31497782 + 1.75 = 3.06497782 x = 3.06497782 Simplifying x = 3.06497782

Subproblem 2

x + -1.75 = -1.31497782 Simplifying x + -1.75 = -1.31497782 Reorder the terms: -1.75 + x = -1.31497782 Solving -1.75 + x = -1.31497782 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.75' to each side of the equation. -1.75 + 1.75 + x = -1.31497782 + 1.75 Combine like terms: -1.75 + 1.75 = 0.00 0.00 + x = -1.31497782 + 1.75 x = -1.31497782 + 1.75 Combine like terms: -1.31497782 + 1.75 = 0.43502218 x = 0.43502218 Simplifying x = 0.43502218

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.06497782, 0.43502218}

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