Difference equations - 2 Multiple choice

[tha boss]

1) Three successive terms of a sequence generated by the difference equation with rule t(n)=t(n-2)
+ t(n-1) are 13,21,x,...
the value of x is
a. 26
b. 29
c. 31
d. 34
e. 42

2) The nth term of a sequence is defined by t(n)= 10(n) + 30, n=1,2,3,..
    This sequence may also be generated by the difference equation
a. t(n+1)=40(n), t1=1
b. t(n+1)=t(n)+ 10, t1= 40
c. t(n+1)=t(n)+10, t1=30
d. t(n+1)=t(n)+30, t1=10
e. t(n+1)= t(n) + 30, t1= 40

[xZero]

1) since x is the 3rd number, n=3, t(3)=t(1)+t(2)=13+21=34 (d)
2) t(n)= 10(n) + 30 means that each number in the sequence is stepped up by 10 each time eg. 40,50,60,70 so its either b or c, now from t(n)= 10(n) + 30, t(1)=40 so it can only be b.

[tha boss]

thanks