x=-3x^2+9x+7

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Solution for x=-3x^2+9x+7 equation:


Simplifying
x = -3x2 + 9x + 7

Reorder the terms:
x = 7 + 9x + -3x2

Solving
x = 7 + 9x + -3x2

Solving for variable 'x'.

Reorder the terms:
-7 + x + -9x + 3x2 = 7 + 9x + -3x2 + -7 + -9x + 3x2

Combine like terms: x + -9x = -8x
-7 + -8x + 3x2 = 7 + 9x + -3x2 + -7 + -9x + 3x2

Reorder the terms:
-7 + -8x + 3x2 = 7 + -7 + 9x + -9x + -3x2 + 3x2

Combine like terms: 7 + -7 = 0
-7 + -8x + 3x2 = 0 + 9x + -9x + -3x2 + 3x2
-7 + -8x + 3x2 = 9x + -9x + -3x2 + 3x2

Combine like terms: 9x + -9x = 0
-7 + -8x + 3x2 = 0 + -3x2 + 3x2
-7 + -8x + 3x2 = -3x2 + 3x2

Combine like terms: -3x2 + 3x2 = 0
-7 + -8x + 3x2 = 0

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

Divide each side by '3'.
-2.333333333 + -2.666666667x + x2 = 0

Move the constant term to the right:

Add '2.333333333' to each side of the equation.
-2.333333333 + -2.666666667x + 2.333333333 + x2 = 0 + 2.333333333

Reorder the terms:
-2.333333333 + 2.333333333 + -2.666666667x + x2 = 0 + 2.333333333

Combine like terms: -2.333333333 + 2.333333333 = 0.000000000
0.000000000 + -2.666666667x + x2 = 0 + 2.333333333
-2.666666667x + x2 = 0 + 2.333333333

Combine like terms: 0 + 2.333333333 = 2.333333333
-2.666666667x + x2 = 2.333333333

The x term is -2.666666667x.  Take half its coefficient (-1.333333334).
Square it (1.777777780) and add it to both sides.

Add '1.777777780' to each side of the equation.
-2.666666667x + 1.777777780 + x2 = 2.333333333 + 1.777777780

Reorder the terms:
1.777777780 + -2.666666667x + x2 = 2.333333333 + 1.777777780

Combine like terms: 2.333333333 + 1.777777780 = 4.111111113
1.777777780 + -2.666666667x + x2 = 4.111111113

Factor a perfect square on the left side:
(x + -1.333333334)(x + -1.333333334) = 4.111111113

Calculate the square root of the right side: 2.027587511

Break this problem into two subproblems by setting 
(x + -1.333333334) equal to 2.027587511 and -2.027587511.

Subproblem 1

x + -1.333333334 = 2.027587511 Simplifying x + -1.333333334 = 2.027587511 Reorder the terms: -1.333333334 + x = 2.027587511 Solving -1.333333334 + x = 2.027587511 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.333333334' to each side of the equation. -1.333333334 + 1.333333334 + x = 2.027587511 + 1.333333334 Combine like terms: -1.333333334 + 1.333333334 = 0.000000000 0.000000000 + x = 2.027587511 + 1.333333334 x = 2.027587511 + 1.333333334 Combine like terms: 2.027587511 + 1.333333334 = 3.360920845 x = 3.360920845 Simplifying x = 3.360920845

Subproblem 2

x + -1.333333334 = -2.027587511 Simplifying x + -1.333333334 = -2.027587511 Reorder the terms: -1.333333334 + x = -2.027587511 Solving -1.333333334 + x = -2.027587511 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.333333334' to each side of the equation. -1.333333334 + 1.333333334 + x = -2.027587511 + 1.333333334 Combine like terms: -1.333333334 + 1.333333334 = 0.000000000 0.000000000 + x = -2.027587511 + 1.333333334 x = -2.027587511 + 1.333333334 Combine like terms: -2.027587511 + 1.333333334 = -0.694254177 x = -0.694254177 Simplifying x = -0.694254177

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.360920845, -0.694254177}

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