Michael is packing his bags for his vacation. He has 6 unique books, but only 4 fit in his bag. How many different groups of 4 books can he take?

15

Step-by-step explanation:

Michael has 6 unique books, but 4 not-unique slots. Since the slot is not unique, the orders you pick the 4 books are not important. When order important you use permutation but since the order is not important you use the combination. The calculation will be:

6C4 = = 15

There are 15 ways to group the 4 books.

hello from mrbilldoesmath!

answer:

x - 3

discussion:

x^2 - 9 = (x-3) (x+3)   so

(x^2-9)/ (x + 3) = x-3

you,

mrb