x^2+3x=-42

Solution for x^2+3x=-42 equation:

Simplifying
x2 + 3x = -42

Reorder the terms:
3x + x2 = -42

Solving
3x + x2 = -42

Solving for variable 'x'.

Reorder the terms:
42 + 3x + x2 = -42 + 42

Combine like terms: -42 + 42 = 0
42 + 3x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '-42' to each side of the equation.
42 + 3x + -42 + x2 = 0 + -42

Reorder the terms:
42 + -42 + 3x + x2 = 0 + -42

Combine like terms: 42 + -42 = 0
0 + 3x + x2 = 0 + -42
3x + x2 = 0 + -42

Combine like terms: 0 + -42 = -42
3x + x2 = -42

The x term is 3x.  Take half its coefficient (1.5).
Square it (2.25) and add it to both sides.

Add '2.25' to each side of the equation.
3x + 2.25 + x2 = -42 + 2.25

Reorder the terms:
2.25 + 3x + x2 = -42 + 2.25

Combine like terms: -42 + 2.25 = -39.75
2.25 + 3x + x2 = -39.75

Factor a perfect square on the left side:
(x + 1.5)(x + 1.5) = -39.75

Can't calculate square root of the right side.

The solution to this equation could not be determined.