9x^2-21x-20=0

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Solution for 9x^2-21x-20=0 equation:


Simplifying
9x2 + -21x + -20 = 0

Reorder the terms:
-20 + -21x + 9x2 = 0

Solving
-20 + -21x + 9x2 = 0

Solving for variable 'x'.

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

Divide each side by '9'.
-2.222222222 + -2.333333333x + x2 = 0

Move the constant term to the right:

Add '2.222222222' to each side of the equation.
-2.222222222 + -2.333333333x + 2.222222222 + x2 = 0 + 2.222222222

Reorder the terms:
-2.222222222 + 2.222222222 + -2.333333333x + x2 = 0 + 2.222222222

Combine like terms: -2.222222222 + 2.222222222 = 0.000000000
0.000000000 + -2.333333333x + x2 = 0 + 2.222222222
-2.333333333x + x2 = 0 + 2.222222222

Combine like terms: 0 + 2.222222222 = 2.222222222
-2.333333333x + x2 = 2.222222222

The x term is -2.333333333x.  Take half its coefficient (-1.166666667).
Square it (1.361111112) and add it to both sides.

Add '1.361111112' to each side of the equation.
-2.333333333x + 1.361111112 + x2 = 2.222222222 + 1.361111112

Reorder the terms:
1.361111112 + -2.333333333x + x2 = 2.222222222 + 1.361111112

Combine like terms: 2.222222222 + 1.361111112 = 3.583333334
1.361111112 + -2.333333333x + x2 = 3.583333334

Factor a perfect square on the left side:
(x + -1.166666667)(x + -1.166666667) = 3.583333334

Calculate the square root of the right side: 1.892969449

Break this problem into two subproblems by setting 
(x + -1.166666667) equal to 1.892969449 and -1.892969449.

Subproblem 1

x + -1.166666667 = 1.892969449 Simplifying x + -1.166666667 = 1.892969449 Reorder the terms: -1.166666667 + x = 1.892969449 Solving -1.166666667 + x = 1.892969449 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.166666667' to each side of the equation. -1.166666667 + 1.166666667 + x = 1.892969449 + 1.166666667 Combine like terms: -1.166666667 + 1.166666667 = 0.000000000 0.000000000 + x = 1.892969449 + 1.166666667 x = 1.892969449 + 1.166666667 Combine like terms: 1.892969449 + 1.166666667 = 3.059636116 x = 3.059636116 Simplifying x = 3.059636116

Subproblem 2

x + -1.166666667 = -1.892969449 Simplifying x + -1.166666667 = -1.892969449 Reorder the terms: -1.166666667 + x = -1.892969449 Solving -1.166666667 + x = -1.892969449 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.166666667' to each side of the equation. -1.166666667 + 1.166666667 + x = -1.892969449 + 1.166666667 Combine like terms: -1.166666667 + 1.166666667 = 0.000000000 0.000000000 + x = -1.892969449 + 1.166666667 x = -1.892969449 + 1.166666667 Combine like terms: -1.892969449 + 1.166666667 = -0.726302782 x = -0.726302782 Simplifying x = -0.726302782

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.059636116, -0.726302782}

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