According to Vieta's Formulas, if

are solutions of a given quadratic equation:
Then:
is the completely factored form of

.
If choose

, then:

So, according to Vieta's formula, we can get:

But

:
Answer:
The sequence is arithmetic
we know that
In an arithmetic sequence, the difference between consecutive terms is always the same and is called common difference
In this problem we have
3,9,15,21,...
Let
a1=3, a2=9,a3=15,a4=21
a4-a3=21-15=6
a3-a2=15-9=6
a2-a1=9-3=6
The sequence is arithmetic
The common difference is equal to
There are 26 letters in the alphabet, 5 are vowels, therefore, the probability of choosing a vowel the first time is:

and the second time is:

Continuing with this reasoning, we get that the probabilities each time are:

Finally, the probability that you get all vowels is the product of the probabilities:

Writing the above result as a percentage we get:

Answer:
1. 256
2. 7^7
3. 46,629
4. 16,649
5. 5^4