In the above example, both x² and 4x can be divided by x.

Therefore x² + 4x can be written as x( __ + __ )

The next step is to figure out what goes in the gaps.

x × __ = x² ? Another x is required in the gap.

x × __ = 4x A 4 is required in the gap.

Hence x² + 4x = x(x+4)