Question

Find the meall, 11
the other numbers.
11./There are four unknown numbers. The mean of the first two numbers is 4 and the
of the first three is 9. The mean of all four number is 15, if one of the four number​

Answer 1

Answer:

give me 5

Step-by-step explanation:

When we multiply this out we will have a sum of terms each of which results from

a choice of an a or b for each of n factors. When we choose j a’s and (n − j) b’s,

we obtain a term of the form aj bn−j . To determine such a term, we have to specify

j of the n terms in the product from which we choose the a. This can be done in

¡n

j

¢

ways. Thus, collecting these terms in the sum contributes a term ¡n

j

¢

aj bn−j . ✷

For example, we have

(a + b)

0 = 1

(a + b)

1 = a + b

(a + b)

2 = a2 + 2ab + b2

(a + b)

3 = a3 + 3a2b + 3ab2 + b3 .

We see here that the coefficients of successive powers do indeed yield Pascal’s tri-

angle