So, in the first case, you have to add 10 numbers together. In the second case, you have to add 20 numbers together. I'm sure you know how to add numbers together, so don't be intimidated by the loop.
In my opinion, the natural way to do this sum is with a "for" loop:
total = 0;
for k=1:n
total = total + ((-1)^k * k^2 +5*k)/3^k;
end
However, you have been told to do this with a "while" loop. Therefore, it is equivalent to write:
total = 0;
k=1;
while k <= n
total = total + ((-1)^k * k^2 +5*k)/3^k;
k = k+1;
end
All you have to do is define "n" as required.
