9x^2-7x=78

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Solution for 9x^2-7x=78 equation:


Simplifying
9x2 + -7x = 78

Reorder the terms:
-7x + 9x2 = 78

Solving
-7x + 9x2 = 78

Solving for variable 'x'.

Reorder the terms:
-78 + -7x + 9x2 = 78 + -78

Combine like terms: 78 + -78 = 0
-78 + -7x + 9x2 = 0

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

Divide each side by '9'.
-8.666666667 + -0.7777777778x + x2 = 0

Move the constant term to the right:

Add '8.666666667' to each side of the equation.
-8.666666667 + -0.7777777778x + 8.666666667 + x2 = 0 + 8.666666667

Reorder the terms:
-8.666666667 + 8.666666667 + -0.7777777778x + x2 = 0 + 8.666666667

Combine like terms: -8.666666667 + 8.666666667 = 0.000000000
0.000000000 + -0.7777777778x + x2 = 0 + 8.666666667
-0.7777777778x + x2 = 0 + 8.666666667

Combine like terms: 0 + 8.666666667 = 8.666666667
-0.7777777778x + x2 = 8.666666667

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 = 8.666666667 + 0.1512345679

Reorder the terms:
0.1512345679 + -0.7777777778x + x2 = 8.666666667 + 0.1512345679

Combine like terms: 8.666666667 + 0.1512345679 = 8.8179012349
0.1512345679 + -0.7777777778x + x2 = 8.8179012349

Factor a perfect square on the left side:
(x + -0.3888888889)(x + -0.3888888889) = 8.8179012349

Calculate the square root of the right side: 2.969495114

Break this problem into two subproblems by setting 
(x + -0.3888888889) equal to 2.969495114 and -2.969495114.

Subproblem 1

x + -0.3888888889 = 2.969495114 Simplifying x + -0.3888888889 = 2.969495114 Reorder the terms: -0.3888888889 + x = 2.969495114 Solving -0.3888888889 + x = 2.969495114 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 = 2.969495114 + 0.3888888889 Combine like terms: -0.3888888889 + 0.3888888889 = 0.0000000000 0.0000000000 + x = 2.969495114 + 0.3888888889 x = 2.969495114 + 0.3888888889 Combine like terms: 2.969495114 + 0.3888888889 = 3.3583840029 x = 3.3583840029 Simplifying x = 3.3583840029

Subproblem 2

x + -0.3888888889 = -2.969495114 Simplifying x + -0.3888888889 = -2.969495114 Reorder the terms: -0.3888888889 + x = -2.969495114 Solving -0.3888888889 + x = -2.969495114 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 = -2.969495114 + 0.3888888889 Combine like terms: -0.3888888889 + 0.3888888889 = 0.0000000000 0.0000000000 + x = -2.969495114 + 0.3888888889 x = -2.969495114 + 0.3888888889 Combine like terms: -2.969495114 + 0.3888888889 = -2.5806062251 x = -2.5806062251 Simplifying x = -2.5806062251

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.3583840029, -2.5806062251}

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