1,3,9,27 what is the next 3 sequence?

This appears to be a geometric sequence with a common ratio of 3. The next three numbers are ...

27*3 = 81

81*3 = 243

243*3 = 729

-7/8

step-by-step explanation:

instead of subtracting you add the -6/8 and -1/8

a 4/6 = 9/12   not proportional

step-by-step explanation:

to find which are not proportional, we can use cross products

if it is true, they are proportional.   if it is not true, they are not proportional.

a 4/6 = 9/12

4* 12 = 6*9

48 = 54

not this is not proportional  

b 2/3 = 12/18  

2* 18 = 3 * 12

36 = 36

this is proportional

c 5/4 = 10/8  

5*8 = 4*10

40 = 40

this is proportional

d 7/5 = 35/25

7*25 = 5 * 35

175 = 175

is proportional