my error when i wrote that x*x or x^2 is not working

n=1:100;
x=0:1;

for i=1:length(n)
  x^2 = mod(x,n(i));

Incorrect use of '=' operator. Assign a value to a variable using '=' and compare values for equality using '=='.

end


i want to get all value of n where x=0 And x = 1 onnnllly

[Voss]

"i want to get all value of n where x=0 or x = 1"

x is [0 1], which is a 1x2 vector that is 0 or 1 everywhere.

n is [1 2 3 ... 99 100].

So the elements of n where x is 0 or 1 are the first two elements of n.

n=1:100;
x=0:1;

n(x == 0 | x == 1)

ans = 1×2

1 2

Is that what you want?

[Mohammed AL Rashedi]

Thank you , but again is true whene n = 7,25,13,.... where x=0 and x=1 .you get only 1 and 2. so,how about it ?

[Voss]

"is true whene n = 7,25,13,...."

What's true when n = 7, 25, 13, ...?

What are you actually trying to do?

[Mohammed AL Rashedi]

Now , let x^2 = x mod 7 then we have only two solution x=0 and x=1.

Simillary ,

let x^2 = x mod 25 then we have only two solution x=0 and x=1.

so now i want to conversely.

let there are two solutions x=0 and x=1 (only) i want to get n (n=7 ,n=25,.....)

Answer 1

[Voss]

Maybe this:

n=1:100;
n_true = [];
for i=1:length(n)
    x = 2:n(i)-1;
    x2 = mod(x.^2,n(i));
    if ~any(x2 == x)
        n_true(end+1) = n(i);
    end
end
disp(n_true);

  Columns 1 through 33

     1     2     3     4     5     7     8     9    11    13    16    17    19    23    25    27    29    31    32    37    41    43    47    49    53    59    61    64    67    71    73    79    81

  Columns 34 through 36

    83    89    97

[Mohammed AL Rashedi]

Thank you .the best