Given:
3,6,9,12,15,18...
We need to find the difference.
The difference between 3 and 6 is 6-3 =3.
The difference between 6 and 9 is 9-6 =3.
The difference between 9 and 12 is 12-9 =3.
The difference between 12 and 15 is 15-12 =3.
The difference between 15 and 18 is 18-15 =3.
Recall that linear have equal differences.
We get an equal difference between each value.
The form of the equation is
Hence the given is linear.