-0.8x^2-3.2x+16.8=

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Solution for -0.8x^2-3.2x+16.8= equation:


Simplifying
-0.8x2 + -3.2x + 16.8 = 0

Reorder the terms:
16.8 + -3.2x + -0.8x2 = 0

Solving
16.8 + -3.2x + -0.8x2 = 0

Solving for variable 'x'.

Begin completing the square.  Divide all terms by
-0.8 the coefficient of the squared term: 

Divide each side by '-0.8'.
-21 + 4x + x2 = 0

Move the constant term to the right:

Add '21' to each side of the equation.
-21 + 4x + 21 + x2 = 0 + 21

Reorder the terms:
-21 + 21 + 4x + x2 = 0 + 21

Combine like terms: -21 + 21 = 0
0 + 4x + x2 = 0 + 21
4x + x2 = 0 + 21

Combine like terms: 0 + 21 = 21
4x + x2 = 21

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 = 21 + 4

Reorder the terms:
4 + 4x + x2 = 21 + 4

Combine like terms: 21 + 4 = 25
4 + 4x + x2 = 25

Factor a perfect square on the left side:
(x + 2)(x + 2) = 25

Calculate the square root of the right side: 5

Break this problem into two subproblems by setting 
(x + 2) equal to 5 and -5.

Subproblem 1

x + 2 = 5 Simplifying x + 2 = 5 Reorder the terms: 2 + x = 5 Solving 2 + x = 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 = 5 + -2 Combine like terms: 2 + -2 = 0 0 + x = 5 + -2 x = 5 + -2 Combine like terms: 5 + -2 = 3 x = 3 Simplifying x = 3

Subproblem 2

x + 2 = -5 Simplifying x + 2 = -5 Reorder the terms: 2 + x = -5 Solving 2 + x = -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 = -5 + -2 Combine like terms: 2 + -2 = 0 0 + x = -5 + -2 x = -5 + -2 Combine like terms: -5 + -2 = -7 x = -7 Simplifying x = -7

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3, -7}

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