which of the following express 1+2+4+8+16+32 in sigma notation?

a.) 2^(k-1) from k=1 to 6

b.) 2^k from k=0 to 5

c.) 2^(k+1) from k= -1 to 4

I don't understand, isn't it all of them??

Also, use formulas to evaluate:

(1-k)*(2-k) from k=0 to k=n

I'm confused on this problem because I only know formulas for summations from k=1 to k=n. Anyone know how to do this one?

Thanks!!