What is the equation for a geometric sequence with a first term of 2 and a second term of -8

The formula of a general term of a sequence is :

y_{n}=ar^{n-1}

Where a= first term, r = common ratio and n= number of terms.

Given first term: a = 2

We can find the common ratio by dividing second term by first term.

So, r= Second term/ first term= -8/2= -4

Next step is to plug in the values of a and r in the above formula to get the equation for geometric sequence.

So, y_{n}=2(-4)^{n-1} is the equation for a geometric sequence .