We have the next numbers
[tex]7,14,28,56[/tex]as we can see we have double of the previous number, so the rule is
[tex]a_n=a_{n-1}\cdot2[/tex]we need to prove the rule
[tex]a1=7[/tex][tex]a2=7\cdot2=14[/tex][tex]a3=14\cdot2=28[/tex][tex]a4=28\cdot2=56[/tex]as we can see the rule is appropriate for the geometric sequence
