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# FP1 Help watch

1. Hi guys,

I wonder if anybody could help me do an FP1 question on Induction ( q.10, p.105, ex.6)

The question is:

"Prove that if Un+2=3Un+1 -2Un for n being an element of the set of natural numbers, and if U1=1 , U2=3, then Un=(2^n)-1."

Could someone please walk me through the steps of the solution? - I have no idea how to do a question with a Un+2 in. I know how to do it if there is an expression connecting Un+1 and Un

Thanks a lot in advance!!
2. This is an induction question with 2 base cases. Usually you have one base case and you have to show that {true for k} implies {true for k+1}, whereas here you need to show that {true for k and k+1} implies {true for k+2}. So check that it holds true for the base cases ( and ), and then check that if it's true for then it's true for .

That is, given that and , show that using the formula.

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