The number of permutations of the 26 letters of the English alphabet that do not contain any of the strings fish, rat, or bird is 402619359782336797900800000
Let

Then

Note that since
, 
But since
, 
and
, 
Since

where 
and

What we are looking for is the number of permutations of the 26 letters of the alphabet that do not contain the strings fish, rat or bird, or

This link contains another solved problem on permutations:
brainly.com/question/7951365
Answer:
Step-by-step explanation:
1. Supplementary
2. complementary
3. neither
4. These two are vertically opposite so neither.
5. Supplementary
6. They add to 90 so they are complementary
7. They add to 180 so they are supplementary.
8. These 2 are equal and vertically opposite. They are neither for this exercise.
9. Complementary: they add to 90.
Answer:
1.001e+17
Step-by-step explanation:
We are asked to determine the limits of the function cos(2x) / x as x approaches to zero. In this case, we first substitute zero to x resulting to 1/0. A number, any number divided by zero is always equal to infinity, Hence there are no limits to this function.