Alien shape patterns
This task is about finding a rule for a growing pattern.
Gerry is using matchsticks to make "alien" shapes. He has made three so far.



Alien 1  Alien 2  Alien 3 
a) 
Draw Alien 4 in the space below.


b) 
Complete the following table.


c) 
Describe, in words, the rule which links the Alien number to the number of matches used.


d) 
Using x for the Alien number and y for the number of matches, write your rule as a formula.
y =__________________________________


e) 
Show how to use your formula to work out the number of matchsticks needed for Alien 21.
