How many triangles can you make from straws with the lengths 2,1,2 inches?
1 answer:
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Answer:
f(n) = f(n - 1) + 3
Step-by-step explanation:
Substitute to get the recursive formula.
OPTION 1: f(n) = f(n - 1) + 3
Substituting n = 1.
f(1) = f(1 - 1) + 3 = 0 + 3 = 3.
Substituting n = 2.
f(2) = f(2 - 1) + 3 = f(1) + 3 = 3 + 3 = 6.
Substituting n = 3.
f(3) = f(3 - 1) + 3 = f(2) + 3 = 6 + 3 = 9.
The numbers match the given sequence. So, we say the above recursive formula represents the sequence.
OPTION 2: f(n) = f(n - 1) + 2
Substituting n = 1
f(1) = f(0) + 2 3.
So, this is eliminated.
Similarly, OPTION 3 and OPTION 4 can be eliminated as well.