x-x^2-12=42

Solution for x-x^2-12=42 equation:

Simplifying
x + -1x2 + -12 = 42

Reorder the terms:
-12 + x + -1x2 = 42

Solving
-12 + x + -1x2 = 42

Solving for variable 'x'.

Reorder the terms:
-12 + -42 + x + -1x2 = 42 + -42

Combine like terms: -12 + -42 = -54
-54 + x + -1x2 = 42 + -42

Combine like terms: 42 + -42 = 0
-54 + x + -1x2 = 0

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

Divide each side by '-1'.
54 + -1x + x2 = 0

Move the constant term to the right:

Add '-54' to each side of the equation.
54 + -1x + -54 + x2 = 0 + -54

Reorder the terms:
54 + -54 + -1x + x2 = 0 + -54

Combine like terms: 54 + -54 = 0
0 + -1x + x2 = 0 + -54
-1x + x2 = 0 + -54

Combine like terms: 0 + -54 = -54
-1x + x2 = -54

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 = -54 + 0.25

Reorder the terms:
0.25 + -1x + x2 = -54 + 0.25

Combine like terms: -54 + 0.25 = -53.75
0.25 + -1x + x2 = -53.75

Factor a perfect square on the left side:
(x + 0.5)(x + 0.5) = -53.75

Can't calculate square root of the right side.

The solution to this equation could not be determined.