Which equation is represented by the table

One way of solving this is simply by substituting for each x in the table into each formula to see if you get the corresponding y in the table

so if x is 1, 
then in the first equation -> y = 1-2(1) = y= 1-2 = -1
so right off the bat, we found the right equation
but essentially you should do it until you find the one that fits

The 1st equation ( y = 1 - 2x) represents the table:
PROOF:
f(1) =1-2 = -1
f(2) = 1-4 = - 3
f(3) = 1-6 = - 5 , etc..

3cm and 6 and 9 cm that a possibility of that question