Question

The sixth term of a sequence is 5. The tenth term is 7.

Which of these position-to-term rules is correct one for the sequence?

A.Term=position number -1
B.Term=2xposition number-7
C.Term=1/2xposition number+2
D.Term=1/6xposition number+4

Answers

  1. Check the possibilities:

    A:

    u(n)=n-1
    u(6)=6–1= True
    u(10)=10–1≠7 False

    A is eliminated.

    B:

    u(n)=2n–7
    u(6)=2(6)–7=12–7=5 True
    u(10)=2(10)–7=20–7≠7 False

    B is eliminated.

    C:

    u(n)=0.5n+2
    u(6)=0.5(6)+2=3+2=5 True
    u(10)=0.5(10)+2=5+2=7 True

    C is your answer.

    Check D although we know it’s C:

    u(n)=n/6 +4
    u(6)=6/6 +4=1+4=5 True
    u(10)=10/6 +4=2.5+4=6.5≠7 False

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