# Math Help - 2, 5, 8, 11, 14... (continued)

1. ## 2, 5, 8, 11, 14... (q1)

Which cube members are not in the sequence and prove it?

2, 5, 8, 11, 14, ...

How can this be proved

2. Originally Posted by Natasha
Which cube members are not in the sequence and prove it?

2, 5, 8, 11, 14, ...

How can this be proved
Thus you want to find,
$3k+2=x^3$
I believe you may state that,
$x^3\equiv 1\mod 3$
if and only if, (there is a $k$ such as)
$3k+2=x^3$.
Thus, all the values of $x$ which are
"cubic residues" which are $1,4,7,10,13,...$
Maybe?