(a + b)^3 = a^3 + 3a^2b + 3ab^2+ b^3
(a +(- b))^3 = (a-b)^2 = a^3 - 3a^2b + 3ab^2- b^3
What do you need help on exactly?
<h2>
Answer:</h2>
<em><u>Recursive equation for the pattern followed is given by,</u></em>

<h2>
Step-by-step explanation:</h2>
In the question,
The number of interaction for 1 child = 0
Number of interactions for 2 children = 1
Number of interactions for 3 children = 5
Number of interaction for 4 children = 14
So,
We need to find out the pattern for the recursive equation for the given conditions.
So,
We see that,

Therefore, on checking, we observe that,

On checking the equation at the given values of 'n' of, 1, 2, 3 and 4.
<u>At, </u>
<u>n = 1</u>

which is true.
<u>At, </u>
<u>n = 2</u>

Which is also true.
<u>At, </u>
<u>n = 3</u>

Which is true.
<u>At, </u>
<u>n = 4</u>

This is also true at the given value of 'n'.
<em><u>Therefore, the recursive equation for the pattern followed is given by,</u></em>

Step-by-step explanation:
You have 5 digits.Youdonot say if duplication is allowed. I will assume not
For the first digit you have 5 choices. One of the 5 digits is gone.
You now have 4 digits to choose from. You pick one. Now you have but 3 left.
The total answer if 5*4*3*2*1 = 120