-3+x(-x)=12+(-x)

Solution for -3+x(-x)=12+(-x) equation:

Simplifying
-3 + x(-1x) = 12 + (-1x)

Remove parenthesis around (-1x)
-3 + x * -1x = 12 + (-1x)

Reorder the terms for easier multiplication:
-3 + -1x * x = 12 + (-1x)

Multiply x * x
-3 + -1x2 = 12 + (-1x)

Solving
-3 + -1x2 = 12 + (-1x)

Solving for variable 'x'.
-3 + -1x2 + -12 + x = 12 + (-1x) + -12 + (x)

Reorder the terms:
-3 + -12 + x + -1x2 = 12 + (-1x) + -12 + (x)

Combine like terms: -3 + -12 = -15
-15 + x + -1x2 = 12 + (-1x) + -12 + (x)
-15 + x + -1x2 = 12 + (-1x) + -12 + x

Reorder the terms:
-15 + x + -1x2 = 12 + -12 + (-1x) + x

Combine like terms: 12 + -12 = 0
-15 + x + -1x2 = 0 + (-1x) + x
-15 + x + -1x2 = (-1x) + x

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

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

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

Move the constant term to the right:

Add '-15' to each side of the equation.
15 + -1x + -15 + x2 = 0 + -15

Reorder the terms:
15 + -15 + -1x + x2 = 0 + -15

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

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

The x term is x.  Take half its coefficient (0.5).
Square it (0.25) and add it to both sides.

Add '0.25' to each side of the equation.
-1x + 0.25 + x2 = -15 + 0.25

Reorder the terms:
0.25 + -1x + x2 = -15 + 0.25

Combine like terms: -15 + 0.25 = -14.75
0.25 + -1x + x2 = -14.75

Factor a perfect square on the left side:
(x + 0.5)(x + 0.5) = -14.75

Can't calculate square root of the right side.

The solution to this equation could not be determined.