40=x(4x)

Solution for 40=x(4x) equation:

Simplifying
40 = x(4x)

Remove parenthesis around (4x)
40 = x * 4x

Reorder the terms for easier multiplication:
40 = 4x * x

Multiply x * x
40 = 4x2

Solving
40 = 4x2

Solving for variable 'x'.

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

Add '-4x2' to each side of the equation.
40 + -4x2 = 4x2 + -4x2

Combine like terms: 4x2 + -4x2 = 0
40 + -4x2 = 0

Add '-40' to each side of the equation.
40 + -40 + -4x2 = 0 + -40

Combine like terms: 40 + -40 = 0
0 + -4x2 = 0 + -40
-4x2 = 0 + -40

Combine like terms: 0 + -40 = -40
-4x2 = -40

Divide each side by '-4'.
x2 = 10

Simplifying
x2 = 10

Take the square root of each side:
x = {-3.16227766, 3.16227766}