[(2x)(x)]+[(4x)(x)]=42

Solution for [(2x)(x)]+[(4x)(x)]=42 equation:

Simplifying
[(2x)(x)] + [(4x)(x)] = 42

Remove parenthesis around (2x)
[2x(x)] + [(4x)(x)] = 42

Multiply x * x
[2x2] + [(4x)(x)] = 42

Remove parenthesis around (4x)
[2x2] + [4x(x)] = 42

Multiply x * x
[2x2] + [4x2] = 42

Combine like terms: [2x2] + [4x2] = 6x2
6x2 = 42

Solving
6x2 = 42

Solving for variable 'x'.

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

Divide each side by '6'.
x2 = 7

Simplifying
x2 = 7

Take the square root of each side:
x = {-2.645751311, 2.645751311}