15x-x^2=81

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Solution for 15x-x^2=81 equation:


Simplifying
15x + -1x2 = 81

Solving
15x + -1x2 = 81

Solving for variable 'x'.

Reorder the terms:
-81 + 15x + -1x2 = 81 + -81

Combine like terms: 81 + -81 = 0
-81 + 15x + -1x2 = 0

Begin completing the square.  Divide all terms by
-1 the coefficient of the squared term: 

Divide each side by '-1'.
81 + -15x + x2 = 0

Move the constant term to the right:

Add '-81' to each side of the equation.
81 + -15x + -81 + x2 = 0 + -81

Reorder the terms:
81 + -81 + -15x + x2 = 0 + -81

Combine like terms: 81 + -81 = 0
0 + -15x + x2 = 0 + -81
-15x + x2 = 0 + -81

Combine like terms: 0 + -81 = -81
-15x + x2 = -81

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 = -81 + 56.25

Reorder the terms:
56.25 + -15x + x2 = -81 + 56.25

Combine like terms: -81 + 56.25 = -24.75
56.25 + -15x + x2 = -24.75

Factor a perfect square on the left side:
(x + -7.5)(x + -7.5) = -24.75

Can't calculate square root of the right side.

The solution to this equation could not be determined.

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