0=-9x^2+7x+8

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Solution for 0=-9x^2+7x+8 equation:


Simplifying
0 = -9x2 + 7x + 8

Reorder the terms:
0 = 8 + 7x + -9x2

Solving
0 = 8 + 7x + -9x2

Solving for variable 'x'.

Combine like terms: 0 + -8 = -8
-8 + -7x + 9x2 = 8 + 7x + -9x2 + -8 + -7x + 9x2

Reorder the terms:
-8 + -7x + 9x2 = 8 + -8 + 7x + -7x + -9x2 + 9x2

Combine like terms: 8 + -8 = 0
-8 + -7x + 9x2 = 0 + 7x + -7x + -9x2 + 9x2
-8 + -7x + 9x2 = 7x + -7x + -9x2 + 9x2

Combine like terms: 7x + -7x = 0
-8 + -7x + 9x2 = 0 + -9x2 + 9x2
-8 + -7x + 9x2 = -9x2 + 9x2

Combine like terms: -9x2 + 9x2 = 0
-8 + -7x + 9x2 = 0

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

Divide each side by '9'.
-0.8888888889 + -0.7777777778x + x2 = 0

Move the constant term to the right:

Add '0.8888888889' to each side of the equation.
-0.8888888889 + -0.7777777778x + 0.8888888889 + x2 = 0 + 0.8888888889

Reorder the terms:
-0.8888888889 + 0.8888888889 + -0.7777777778x + x2 = 0 + 0.8888888889

Combine like terms: -0.8888888889 + 0.8888888889 = 0.0000000000
0.0000000000 + -0.7777777778x + x2 = 0 + 0.8888888889
-0.7777777778x + x2 = 0 + 0.8888888889

Combine like terms: 0 + 0.8888888889 = 0.8888888889
-0.7777777778x + x2 = 0.8888888889

The x term is -0.7777777778x.  Take half its coefficient (-0.3888888889).
Square it (0.1512345679) and add it to both sides.

Add '0.1512345679' to each side of the equation.
-0.7777777778x + 0.1512345679 + x2 = 0.8888888889 + 0.1512345679

Reorder the terms:
0.1512345679 + -0.7777777778x + x2 = 0.8888888889 + 0.1512345679

Combine like terms: 0.8888888889 + 0.1512345679 = 1.0401234568
0.1512345679 + -0.7777777778x + x2 = 1.0401234568

Factor a perfect square on the left side:
(x + -0.3888888889)(x + -0.3888888889) = 1.0401234568

Calculate the square root of the right side: 1.019864431

Break this problem into two subproblems by setting 
(x + -0.3888888889) equal to 1.019864431 and -1.019864431.

Subproblem 1

x + -0.3888888889 = 1.019864431 Simplifying x + -0.3888888889 = 1.019864431 Reorder the terms: -0.3888888889 + x = 1.019864431 Solving -0.3888888889 + x = 1.019864431 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.3888888889' to each side of the equation. -0.3888888889 + 0.3888888889 + x = 1.019864431 + 0.3888888889 Combine like terms: -0.3888888889 + 0.3888888889 = 0.0000000000 0.0000000000 + x = 1.019864431 + 0.3888888889 x = 1.019864431 + 0.3888888889 Combine like terms: 1.019864431 + 0.3888888889 = 1.4087533199 x = 1.4087533199 Simplifying x = 1.4087533199

Subproblem 2

x + -0.3888888889 = -1.019864431 Simplifying x + -0.3888888889 = -1.019864431 Reorder the terms: -0.3888888889 + x = -1.019864431 Solving -0.3888888889 + x = -1.019864431 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.3888888889' to each side of the equation. -0.3888888889 + 0.3888888889 + x = -1.019864431 + 0.3888888889 Combine like terms: -0.3888888889 + 0.3888888889 = 0.0000000000 0.0000000000 + x = -1.019864431 + 0.3888888889 x = -1.019864431 + 0.3888888889 Combine like terms: -1.019864431 + 0.3888888889 = -0.6309755421 x = -0.6309755421 Simplifying x = -0.6309755421

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.4087533199, -0.6309755421}

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