13x^2-21x-8=0

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Solution for 13x^2-21x-8=0 equation:


Simplifying
13x2 + -21x + -8 = 0

Reorder the terms:
-8 + -21x + 13x2 = 0

Solving
-8 + -21x + 13x2 = 0

Solving for variable 'x'.

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

Divide each side by '13'.
-0.6153846154 + -1.615384615x + x2 = 0

Move the constant term to the right:

Add '0.6153846154' to each side of the equation.
-0.6153846154 + -1.615384615x + 0.6153846154 + x2 = 0 + 0.6153846154

Reorder the terms:
-0.6153846154 + 0.6153846154 + -1.615384615x + x2 = 0 + 0.6153846154

Combine like terms: -0.6153846154 + 0.6153846154 = 0.0000000000
0.0000000000 + -1.615384615x + x2 = 0 + 0.6153846154
-1.615384615x + x2 = 0 + 0.6153846154

Combine like terms: 0 + 0.6153846154 = 0.6153846154
-1.615384615x + x2 = 0.6153846154

The x term is -1.615384615x.  Take half its coefficient (-0.8076923075).
Square it (0.6523668636) and add it to both sides.

Add '0.6523668636' to each side of the equation.
-1.615384615x + 0.6523668636 + x2 = 0.6153846154 + 0.6523668636

Reorder the terms:
0.6523668636 + -1.615384615x + x2 = 0.6153846154 + 0.6523668636

Combine like terms: 0.6153846154 + 0.6523668636 = 1.267751479
0.6523668636 + -1.615384615x + x2 = 1.267751479

Factor a perfect square on the left side:
(x + -0.8076923075)(x + -0.8076923075) = 1.267751479

Calculate the square root of the right side: 1.125944705

Break this problem into two subproblems by setting 
(x + -0.8076923075) equal to 1.125944705 and -1.125944705.

Subproblem 1

x + -0.8076923075 = 1.125944705 Simplifying x + -0.8076923075 = 1.125944705 Reorder the terms: -0.8076923075 + x = 1.125944705 Solving -0.8076923075 + x = 1.125944705 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.8076923075' to each side of the equation. -0.8076923075 + 0.8076923075 + x = 1.125944705 + 0.8076923075 Combine like terms: -0.8076923075 + 0.8076923075 = 0.0000000000 0.0000000000 + x = 1.125944705 + 0.8076923075 x = 1.125944705 + 0.8076923075 Combine like terms: 1.125944705 + 0.8076923075 = 1.9336370125 x = 1.9336370125 Simplifying x = 1.9336370125

Subproblem 2

x + -0.8076923075 = -1.125944705 Simplifying x + -0.8076923075 = -1.125944705 Reorder the terms: -0.8076923075 + x = -1.125944705 Solving -0.8076923075 + x = -1.125944705 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.8076923075' to each side of the equation. -0.8076923075 + 0.8076923075 + x = -1.125944705 + 0.8076923075 Combine like terms: -0.8076923075 + 0.8076923075 = 0.0000000000 0.0000000000 + x = -1.125944705 + 0.8076923075 x = -1.125944705 + 0.8076923075 Combine like terms: -1.125944705 + 0.8076923075 = -0.3182523975 x = -0.3182523975 Simplifying x = -0.3182523975

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.9336370125, -0.3182523975}

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