Atennis club has 2n members. we want to pair up the members by twos for singles matches. in how many ways can we pair up all the members of the club? suppose that in addition to specifying who plays whom, we also determine who serves first for each pairing. now in how many ways can we specify our pairs? stein, cliff l. discrete mathematics for computer scientists (p. 21). pearson he, inc.. kindle edition.'

the direct variation says that:

then the equation is of the form is given by:

            where k is the constant variation.

from the given table:

consider any value of x and m(x)=y

x = 2 and m(x)=y = 3

substitute these value in [1]; we have;

divide both sides by 2 we get;

⇒

check:

put x = -1 and m(x) = -1.5

substitute in the equation:

-1.5 = -1.5                   true

therefore, the function m(x) represents a direct variation

graph of this function as shown below: