9x^2+5x=21

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Solution for 9x^2+5x=21 equation:


Simplifying
9x2 + 5x = 21

Reorder the terms:
5x + 9x2 = 21

Solving
5x + 9x2 = 21

Solving for variable 'x'.

Reorder the terms:
-21 + 5x + 9x2 = 21 + -21

Combine like terms: 21 + -21 = 0
-21 + 5x + 9x2 = 0

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

Divide each side by '9'.
-2.333333333 + 0.5555555556x + x2 = 0

Move the constant term to the right:

Add '2.333333333' to each side of the equation.
-2.333333333 + 0.5555555556x + 2.333333333 + x2 = 0 + 2.333333333

Reorder the terms:
-2.333333333 + 2.333333333 + 0.5555555556x + x2 = 0 + 2.333333333

Combine like terms: -2.333333333 + 2.333333333 = 0.000000000
0.000000000 + 0.5555555556x + x2 = 0 + 2.333333333
0.5555555556x + x2 = 0 + 2.333333333

Combine like terms: 0 + 2.333333333 = 2.333333333
0.5555555556x + x2 = 2.333333333

The x term is 0.5555555556x.  Take half its coefficient (0.2777777778).
Square it (0.07716049384) and add it to both sides.

Add '0.07716049384' to each side of the equation.
0.5555555556x + 0.07716049384 + x2 = 2.333333333 + 0.07716049384

Reorder the terms:
0.07716049384 + 0.5555555556x + x2 = 2.333333333 + 0.07716049384

Combine like terms: 2.333333333 + 0.07716049384 = 2.41049382684
0.07716049384 + 0.5555555556x + x2 = 2.41049382684

Factor a perfect square on the left side:
(x + 0.2777777778)(x + 0.2777777778) = 2.41049382684

Calculate the square root of the right side: 1.552576512

Break this problem into two subproblems by setting 
(x + 0.2777777778) equal to 1.552576512 and -1.552576512.

Subproblem 1

x + 0.2777777778 = 1.552576512 Simplifying x + 0.2777777778 = 1.552576512 Reorder the terms: 0.2777777778 + x = 1.552576512 Solving 0.2777777778 + x = 1.552576512 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.2777777778' to each side of the equation. 0.2777777778 + -0.2777777778 + x = 1.552576512 + -0.2777777778 Combine like terms: 0.2777777778 + -0.2777777778 = 0.0000000000 0.0000000000 + x = 1.552576512 + -0.2777777778 x = 1.552576512 + -0.2777777778 Combine like terms: 1.552576512 + -0.2777777778 = 1.2747987342 x = 1.2747987342 Simplifying x = 1.2747987342

Subproblem 2

x + 0.2777777778 = -1.552576512 Simplifying x + 0.2777777778 = -1.552576512 Reorder the terms: 0.2777777778 + x = -1.552576512 Solving 0.2777777778 + x = -1.552576512 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.2777777778' to each side of the equation. 0.2777777778 + -0.2777777778 + x = -1.552576512 + -0.2777777778 Combine like terms: 0.2777777778 + -0.2777777778 = 0.0000000000 0.0000000000 + x = -1.552576512 + -0.2777777778 x = -1.552576512 + -0.2777777778 Combine like terms: -1.552576512 + -0.2777777778 = -1.8303542898 x = -1.8303542898 Simplifying x = -1.8303542898

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.2747987342, -1.8303542898}

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