x=-0.2x^2+8x+9

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Solution for x=-0.2x^2+8x+9 equation:


Simplifying
x = -0.2x2 + 8x + 9

Reorder the terms:
x = 9 + 8x + -0.2x2

Solving
x = 9 + 8x + -0.2x2

Solving for variable 'x'.

Reorder the terms:
-9 + x + -8x + 0.2x2 = 9 + 8x + -0.2x2 + -9 + -8x + 0.2x2

Combine like terms: x + -8x = -7x
-9 + -7x + 0.2x2 = 9 + 8x + -0.2x2 + -9 + -8x + 0.2x2

Reorder the terms:
-9 + -7x + 0.2x2 = 9 + -9 + 8x + -8x + -0.2x2 + 0.2x2

Combine like terms: 9 + -9 = 0
-9 + -7x + 0.2x2 = 0 + 8x + -8x + -0.2x2 + 0.2x2
-9 + -7x + 0.2x2 = 8x + -8x + -0.2x2 + 0.2x2

Combine like terms: 8x + -8x = 0
-9 + -7x + 0.2x2 = 0 + -0.2x2 + 0.2x2
-9 + -7x + 0.2x2 = -0.2x2 + 0.2x2

Combine like terms: -0.2x2 + 0.2x2 = 0.0
-9 + -7x + 0.2x2 = 0.0

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

Divide each side by '0.2'.
-45 + -35x + x2 = 0

Move the constant term to the right:

Add '45' to each side of the equation.
-45 + -35x + 45 + x2 = 0 + 45

Reorder the terms:
-45 + 45 + -35x + x2 = 0 + 45

Combine like terms: -45 + 45 = 0
0 + -35x + x2 = 0 + 45
-35x + x2 = 0 + 45

Combine like terms: 0 + 45 = 45
-35x + x2 = 45

The x term is -35x.  Take half its coefficient (-17.5).
Square it (306.25) and add it to both sides.

Add '306.25' to each side of the equation.
-35x + 306.25 + x2 = 45 + 306.25

Reorder the terms:
306.25 + -35x + x2 = 45 + 306.25

Combine like terms: 45 + 306.25 = 351.25
306.25 + -35x + x2 = 351.25

Factor a perfect square on the left side:
(x + -17.5)(x + -17.5) = 351.25

Calculate the square root of the right side: 18.741664814

Break this problem into two subproblems by setting 
(x + -17.5) equal to 18.741664814 and -18.741664814.

Subproblem 1

x + -17.5 = 18.741664814 Simplifying x + -17.5 = 18.741664814 Reorder the terms: -17.5 + x = 18.741664814 Solving -17.5 + x = 18.741664814 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '17.5' to each side of the equation. -17.5 + 17.5 + x = 18.741664814 + 17.5 Combine like terms: -17.5 + 17.5 = 0.0 0.0 + x = 18.741664814 + 17.5 x = 18.741664814 + 17.5 Combine like terms: 18.741664814 + 17.5 = 36.241664814 x = 36.241664814 Simplifying x = 36.241664814

Subproblem 2

x + -17.5 = -18.741664814 Simplifying x + -17.5 = -18.741664814 Reorder the terms: -17.5 + x = -18.741664814 Solving -17.5 + x = -18.741664814 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '17.5' to each side of the equation. -17.5 + 17.5 + x = -18.741664814 + 17.5 Combine like terms: -17.5 + 17.5 = 0.0 0.0 + x = -18.741664814 + 17.5 x = -18.741664814 + 17.5 Combine like terms: -18.741664814 + 17.5 = -1.241664814 x = -1.241664814 Simplifying x = -1.241664814

Solution

The solution to the problem is based on the solutions from the subproblems. x = {36.241664814, -1.241664814}

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