6x^2-5x-21=20

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Solution for 6x^2-5x-21=20 equation:


Simplifying
6x2 + -5x + -21 = 20

Reorder the terms:
-21 + -5x + 6x2 = 20

Solving
-21 + -5x + 6x2 = 20

Solving for variable 'x'.

Reorder the terms:
-21 + -20 + -5x + 6x2 = 20 + -20

Combine like terms: -21 + -20 = -41
-41 + -5x + 6x2 = 20 + -20

Combine like terms: 20 + -20 = 0
-41 + -5x + 6x2 = 0

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

Divide each side by '6'.
-6.833333333 + -0.8333333333x + x2 = 0

Move the constant term to the right:

Add '6.833333333' to each side of the equation.
-6.833333333 + -0.8333333333x + 6.833333333 + x2 = 0 + 6.833333333

Reorder the terms:
-6.833333333 + 6.833333333 + -0.8333333333x + x2 = 0 + 6.833333333

Combine like terms: -6.833333333 + 6.833333333 = 0.000000000
0.000000000 + -0.8333333333x + x2 = 0 + 6.833333333
-0.8333333333x + x2 = 0 + 6.833333333

Combine like terms: 0 + 6.833333333 = 6.833333333
-0.8333333333x + x2 = 6.833333333

The x term is -0.8333333333x.  Take half its coefficient (-0.4166666667).
Square it (0.1736111111) and add it to both sides.

Add '0.1736111111' to each side of the equation.
-0.8333333333x + 0.1736111111 + x2 = 6.833333333 + 0.1736111111

Reorder the terms:
0.1736111111 + -0.8333333333x + x2 = 6.833333333 + 0.1736111111

Combine like terms: 6.833333333 + 0.1736111111 = 7.0069444441
0.1736111111 + -0.8333333333x + x2 = 7.0069444441

Factor a perfect square on the left side:
(x + -0.4166666667)(x + -0.4166666667) = 7.0069444441

Calculate the square root of the right side: 2.647063362

Break this problem into two subproblems by setting 
(x + -0.4166666667) equal to 2.647063362 and -2.647063362.

Subproblem 1

x + -0.4166666667 = 2.647063362 Simplifying x + -0.4166666667 = 2.647063362 Reorder the terms: -0.4166666667 + x = 2.647063362 Solving -0.4166666667 + x = 2.647063362 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.4166666667' to each side of the equation. -0.4166666667 + 0.4166666667 + x = 2.647063362 + 0.4166666667 Combine like terms: -0.4166666667 + 0.4166666667 = 0.0000000000 0.0000000000 + x = 2.647063362 + 0.4166666667 x = 2.647063362 + 0.4166666667 Combine like terms: 2.647063362 + 0.4166666667 = 3.0637300287 x = 3.0637300287 Simplifying x = 3.0637300287

Subproblem 2

x + -0.4166666667 = -2.647063362 Simplifying x + -0.4166666667 = -2.647063362 Reorder the terms: -0.4166666667 + x = -2.647063362 Solving -0.4166666667 + x = -2.647063362 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.4166666667' to each side of the equation. -0.4166666667 + 0.4166666667 + x = -2.647063362 + 0.4166666667 Combine like terms: -0.4166666667 + 0.4166666667 = 0.0000000000 0.0000000000 + x = -2.647063362 + 0.4166666667 x = -2.647063362 + 0.4166666667 Combine like terms: -2.647063362 + 0.4166666667 = -2.2303966953 x = -2.2303966953 Simplifying x = -2.2303966953

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.0637300287, -2.2303966953}

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