-2*x*x+8x+16.5=0

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Solution for -2*x*x+8x+16.5=0 equation:


Simplifying
-2x * x + 8x + 16.5 = 0

Multiply x * x
-2x2 + 8x + 16.5 = 0

Reorder the terms:
16.5 + 8x + -2x2 = 0

Solving
16.5 + 8x + -2x2 = 0

Solving for variable 'x'.

Begin completing the square.  Divide all terms by
-2 the coefficient of the squared term: 

Divide each side by '-2'.
-8.25 + -4x + x2 = 0

Move the constant term to the right:

Add '8.25' to each side of the equation.
-8.25 + -4x + 8.25 + x2 = 0 + 8.25

Reorder the terms:
-8.25 + 8.25 + -4x + x2 = 0 + 8.25

Combine like terms: -8.25 + 8.25 = 0.00
0.00 + -4x + x2 = 0 + 8.25
-4x + x2 = 0 + 8.25

Combine like terms: 0 + 8.25 = 8.25
-4x + x2 = 8.25

The x term is -4x.  Take half its coefficient (-2).
Square it (4) and add it to both sides.

Add '4' to each side of the equation.
-4x + 4 + x2 = 8.25 + 4

Reorder the terms:
4 + -4x + x2 = 8.25 + 4

Combine like terms: 8.25 + 4 = 12.25
4 + -4x + x2 = 12.25

Factor a perfect square on the left side:
(x + -2)(x + -2) = 12.25

Calculate the square root of the right side: 3.5

Break this problem into two subproblems by setting 
(x + -2) equal to 3.5 and -3.5.

Subproblem 1

x + -2 = 3.5 Simplifying x + -2 = 3.5 Reorder the terms: -2 + x = 3.5 Solving -2 + x = 3.5 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2' to each side of the equation. -2 + 2 + x = 3.5 + 2 Combine like terms: -2 + 2 = 0 0 + x = 3.5 + 2 x = 3.5 + 2 Combine like terms: 3.5 + 2 = 5.5 x = 5.5 Simplifying x = 5.5

Subproblem 2

x + -2 = -3.5 Simplifying x + -2 = -3.5 Reorder the terms: -2 + x = -3.5 Solving -2 + x = -3.5 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2' to each side of the equation. -2 + 2 + x = -3.5 + 2 Combine like terms: -2 + 2 = 0 0 + x = -3.5 + 2 x = -3.5 + 2 Combine like terms: -3.5 + 2 = -1.5 x = -1.5 Simplifying x = -1.5

Solution

The solution to the problem is based on the solutions from the subproblems. x = {5.5, -1.5}

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