-.8x^2+12x+25.8=0

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Solution for -.8x^2+12x+25.8=0 equation:


Simplifying
-0.8x2 + 12x + 25.8 = 0

Reorder the terms:
25.8 + 12x + -0.8x2 = 0

Solving
25.8 + 12x + -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'.
-32.25 + -15x + x2 = 0

Move the constant term to the right:

Add '32.25' to each side of the equation.
-32.25 + -15x + 32.25 + x2 = 0 + 32.25

Reorder the terms:
-32.25 + 32.25 + -15x + x2 = 0 + 32.25

Combine like terms: -32.25 + 32.25 = 0.00
0.00 + -15x + x2 = 0 + 32.25
-15x + x2 = 0 + 32.25

Combine like terms: 0 + 32.25 = 32.25
-15x + x2 = 32.25

The x term is -15x.  Take half its coefficient (-7.5).
Square it (56.25) and add it to both sides.

Add '56.25' to each side of the equation.
-15x + 56.25 + x2 = 32.25 + 56.25

Reorder the terms:
56.25 + -15x + x2 = 32.25 + 56.25

Combine like terms: 32.25 + 56.25 = 88.5
56.25 + -15x + x2 = 88.5

Factor a perfect square on the left side:
(x + -7.5)(x + -7.5) = 88.5

Calculate the square root of the right side: 9.407443861

Break this problem into two subproblems by setting 
(x + -7.5) equal to 9.407443861 and -9.407443861.

Subproblem 1

x + -7.5 = 9.407443861 Simplifying x + -7.5 = 9.407443861 Reorder the terms: -7.5 + x = 9.407443861 Solving -7.5 + x = 9.407443861 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '7.5' to each side of the equation. -7.5 + 7.5 + x = 9.407443861 + 7.5 Combine like terms: -7.5 + 7.5 = 0.0 0.0 + x = 9.407443861 + 7.5 x = 9.407443861 + 7.5 Combine like terms: 9.407443861 + 7.5 = 16.907443861 x = 16.907443861 Simplifying x = 16.907443861

Subproblem 2

x + -7.5 = -9.407443861 Simplifying x + -7.5 = -9.407443861 Reorder the terms: -7.5 + x = -9.407443861 Solving -7.5 + x = -9.407443861 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '7.5' to each side of the equation. -7.5 + 7.5 + x = -9.407443861 + 7.5 Combine like terms: -7.5 + 7.5 = 0.0 0.0 + x = -9.407443861 + 7.5 x = -9.407443861 + 7.5 Combine like terms: -9.407443861 + 7.5 = -1.907443861 x = -1.907443861 Simplifying x = -1.907443861

Solution

The solution to the problem is based on the solutions from the subproblems. x = {16.907443861, -1.907443861}

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