400=x*x+42

Solution for 400=x*x+42 equation:

Simplifying
400 = x * x + 42

Multiply x * x
400 = x2 + 42

Reorder the terms:
400 = 42 + x2

Solving
400 = 42 + x2

Solving for variable 'x'.

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

Add '-1x2' to each side of the equation.
400 + -1x2 = 42 + x2 + -1x2

Combine like terms: x2 + -1x2 = 0
400 + -1x2 = 42 + 0
400 + -1x2 = 42

Add '-400' to each side of the equation.
400 + -400 + -1x2 = 42 + -400

Combine like terms: 400 + -400 = 0
0 + -1x2 = 42 + -400
-1x2 = 42 + -400

Combine like terms: 42 + -400 = -358
-1x2 = -358

Divide each side by '-1'.
x2 = 358

Simplifying
x2 = 358

Take the square root of each side:
x = {-18.920887928, 18.920887928}