Hello,
I'm stuck and I can't solve one problem. I've been trying for a few days and have no more ideas.
The sum is defined by: sn=2+8+24+...+n2n
Find simplified expression for the following: tn=n+2(n-1)+4(n-2)+8(n-3)+...+2n-11
I've come to the point:
tn=(n+2n+4n+...+2n)-(2+8+24+...+2nn)=n(-1)-sn=-n-sn
Where I've calculated -1 from the formula for the sum of the infinite geometric sequence. The answer key says: "2n+1-n-2". I don't know how to get there. I'd appreciate someone's help.
I'm stuck and I can't solve one problem. I've been trying for a few days and have no more ideas.
The sum is defined by: sn=2+8+24+...+n2n
Find simplified expression for the following: tn=n+2(n-1)+4(n-2)+8(n-3)+...+2n-11
I've come to the point:
tn=(n+2n+4n+...+2n)-(2+8+24+...+2nn)=n(-1)-sn=-n-sn
Where I've calculated -1 from the formula for the sum of the infinite geometric sequence. The answer key says: "2n+1-n-2". I don't know how to get there. I'd appreciate someone's help.