3x^2+15-42=0

Solution for 3x^2+15-42=0 equation:

Simplifying
3x2 + 15 + -42 = 0

Reorder the terms:
15 + -42 + 3x2 = 0

Combine like terms: 15 + -42 = -27
-27 + 3x2 = 0

Solving
-27 + 3x2 = 0

Solving for variable 'x'.

Move all terms containing x to the left, all other terms to the right.

Add '27' to each side of the equation.
-27 + 27 + 3x2 = 0 + 27

Combine like terms: -27 + 27 = 0
0 + 3x2 = 0 + 27
3x2 = 0 + 27

Combine like terms: 0 + 27 = 27
3x2 = 27

Divide each side by '3'.
x2 = 9

Simplifying
x2 = 9

Take the square root of each side:
x = {-3, 3}