using the while command

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francesca
francesca 2013-5-8
By using the while command, I have to determine the number of terms needed so that the product 2x4x6x8...x2n exceeds a given number N (input by the user). The following is what I tried but it doesn't seem to work.
function y=question2(i,n);
N=input('Enter number N: ')
for i=1:1:n
question2=2*(i)
while question2<=N
question2=question2*(i+1)
display(n)
end
end
Thanks in advance.

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采纳的回答

Azzi Abdelmalek
Azzi Abdelmalek 2013-5-8
编辑：Azzi Abdelmalek 2013-5-8
You should use only while loop (remove the for loop), then increment the variable i inside the while loop (i=i+2).

更多回答（2 个）

David Sanchez
David Sanchez 2013-5-8
Hello Francesca, firstly, why do you use "i" as a input variable? Since you use "i" as index within the for-loop, the input "i" will not be used. (advice: try to avoid using "i" as loop index to avoid confusing with imaginary unit) Second: do not forget to add semicolons (;) at the end of each line, it will produce a cleaner result, unless you want lots of useless information on the command windows. Before attempting anything, try to determine what your input variables will be.
David Sanchez
David Sanchez 2013-5-8
try this code, but remember that we are not here to do your homework.
N = input('Enter number N: ');
n = 2;
r = 2;
count = 0;
while r < N
count = count + 1;
n = n + 2;
r = 2*n;
end
disp(count)

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