The third term in a sequence is 11.
The term-to-term rule is "take away 4".
Write an expression, in terms of n, for the nth term of the sequence.
The third number is 12

Since the person hasn't specified I'll solve for both f(3) = 12 and f(3) = 11.

f(n) = 20 - 4(fn-1) is the formula for when third term is 12

f(n) = 21 -4(n-1) when f(3) = 11

Step-by-step explanation:

Okay since we know d = -4, we can start to make an explicit rule.

But first, we need the first term.

If f(3) = 12, we know f(1) = 20

So.

f(n) = 20 - 4(n-1) when f(3) = 12

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For f(3) = 11, we know f(1) = 21

So.

f(n) = 21 -4(n-1) when f(3) = 11

we don't have enough info to solve this