if n is a natural number , then ( 6 n 2 + 6 n ) is always divisible by ?
"( 6 n 2 + 6 n ) = 6 n ( n + 1 ) , which is always divisible by 6 and 12 both , since n ( n + 1 ) is always even . b )"
add(multiply(6, const_100), multiply(2, 6))