0=-9x^2+8x+9

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Solution for 0=-9x^2+8x+9 equation:


Simplifying
0 = -9x2 + 8x + 9

Reorder the terms:
0 = 9 + 8x + -9x2

Solving
0 = 9 + 8x + -9x2

Solving for variable 'x'.

Combine like terms: 0 + -9 = -9
-9 + -8x + 9x2 = 9 + 8x + -9x2 + -9 + -8x + 9x2

Reorder the terms:
-9 + -8x + 9x2 = 9 + -9 + 8x + -8x + -9x2 + 9x2

Combine like terms: 9 + -9 = 0
-9 + -8x + 9x2 = 0 + 8x + -8x + -9x2 + 9x2
-9 + -8x + 9x2 = 8x + -8x + -9x2 + 9x2

Combine like terms: 8x + -8x = 0
-9 + -8x + 9x2 = 0 + -9x2 + 9x2
-9 + -8x + 9x2 = -9x2 + 9x2

Combine like terms: -9x2 + 9x2 = 0
-9 + -8x + 9x2 = 0

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

Divide each side by '9'.
-1 + -0.8888888889x + x2 = 0

Move the constant term to the right:

Add '1' to each side of the equation.
-1 + -0.8888888889x + 1 + x2 = 0 + 1

Reorder the terms:
-1 + 1 + -0.8888888889x + x2 = 0 + 1

Combine like terms: -1 + 1 = 0
0 + -0.8888888889x + x2 = 0 + 1
-0.8888888889x + x2 = 0 + 1

Combine like terms: 0 + 1 = 1
-0.8888888889x + x2 = 1

The x term is -0.8888888889x.  Take half its coefficient (-0.4444444445).
Square it (0.1975308642) and add it to both sides.

Add '0.1975308642' to each side of the equation.
-0.8888888889x + 0.1975308642 + x2 = 1 + 0.1975308642

Reorder the terms:
0.1975308642 + -0.8888888889x + x2 = 1 + 0.1975308642

Combine like terms: 1 + 0.1975308642 = 1.1975308642
0.1975308642 + -0.8888888889x + x2 = 1.1975308642

Factor a perfect square on the left side:
(x + -0.4444444445)(x + -0.4444444445) = 1.1975308642

Calculate the square root of the right side: 1.094317534

Break this problem into two subproblems by setting 
(x + -0.4444444445) equal to 1.094317534 and -1.094317534.

Subproblem 1

x + -0.4444444445 = 1.094317534 Simplifying x + -0.4444444445 = 1.094317534 Reorder the terms: -0.4444444445 + x = 1.094317534 Solving -0.4444444445 + x = 1.094317534 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.4444444445' to each side of the equation. -0.4444444445 + 0.4444444445 + x = 1.094317534 + 0.4444444445 Combine like terms: -0.4444444445 + 0.4444444445 = 0.0000000000 0.0000000000 + x = 1.094317534 + 0.4444444445 x = 1.094317534 + 0.4444444445 Combine like terms: 1.094317534 + 0.4444444445 = 1.5387619785 x = 1.5387619785 Simplifying x = 1.5387619785

Subproblem 2

x + -0.4444444445 = -1.094317534 Simplifying x + -0.4444444445 = -1.094317534 Reorder the terms: -0.4444444445 + x = -1.094317534 Solving -0.4444444445 + x = -1.094317534 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.4444444445' to each side of the equation. -0.4444444445 + 0.4444444445 + x = -1.094317534 + 0.4444444445 Combine like terms: -0.4444444445 + 0.4444444445 = 0.0000000000 0.0000000000 + x = -1.094317534 + 0.4444444445 x = -1.094317534 + 0.4444444445 Combine like terms: -1.094317534 + 0.4444444445 = -0.6498730895 x = -0.6498730895 Simplifying x = -0.6498730895

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.5387619785, -0.6498730895}

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