2x^2-31x+21=0

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Solution for 2x^2-31x+21=0 equation:


Simplifying
2x2 + -31x + 21 = 0

Reorder the terms:
21 + -31x + 2x2 = 0

Solving
21 + -31x + 2x2 = 0

Solving for variable 'x'.

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

Divide each side by '2'.
10.5 + -15.5x + x2 = 0

Move the constant term to the right:

Add '-10.5' to each side of the equation.
10.5 + -15.5x + -10.5 + x2 = 0 + -10.5

Reorder the terms:
10.5 + -10.5 + -15.5x + x2 = 0 + -10.5

Combine like terms: 10.5 + -10.5 = 0.0
0.0 + -15.5x + x2 = 0 + -10.5
-15.5x + x2 = 0 + -10.5

Combine like terms: 0 + -10.5 = -10.5
-15.5x + x2 = -10.5

The x term is -15.5x.  Take half its coefficient (-7.75).
Square it (60.0625) and add it to both sides.

Add '60.0625' to each side of the equation.
-15.5x + 60.0625 + x2 = -10.5 + 60.0625

Reorder the terms:
60.0625 + -15.5x + x2 = -10.5 + 60.0625

Combine like terms: -10.5 + 60.0625 = 49.5625
60.0625 + -15.5x + x2 = 49.5625

Factor a perfect square on the left side:
(x + -7.75)(x + -7.75) = 49.5625

Calculate the square root of the right side: 7.04006392

Break this problem into two subproblems by setting 
(x + -7.75) equal to 7.04006392 and -7.04006392.

Subproblem 1

x + -7.75 = 7.04006392 Simplifying x + -7.75 = 7.04006392 Reorder the terms: -7.75 + x = 7.04006392 Solving -7.75 + x = 7.04006392 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '7.75' to each side of the equation. -7.75 + 7.75 + x = 7.04006392 + 7.75 Combine like terms: -7.75 + 7.75 = 0.00 0.00 + x = 7.04006392 + 7.75 x = 7.04006392 + 7.75 Combine like terms: 7.04006392 + 7.75 = 14.79006392 x = 14.79006392 Simplifying x = 14.79006392

Subproblem 2

x + -7.75 = -7.04006392 Simplifying x + -7.75 = -7.04006392 Reorder the terms: -7.75 + x = -7.04006392 Solving -7.75 + x = -7.04006392 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '7.75' to each side of the equation. -7.75 + 7.75 + x = -7.04006392 + 7.75 Combine like terms: -7.75 + 7.75 = 0.00 0.00 + x = -7.04006392 + 7.75 x = -7.04006392 + 7.75 Combine like terms: -7.04006392 + 7.75 = 0.70993608 x = 0.70993608 Simplifying x = 0.70993608

Solution

The solution to the problem is based on the solutions from the subproblems. x = {14.79006392, 0.70993608}

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