# Q: Let S = {1,2,5,6 } Define a relation R on S of at least four order pairs, as (a,b)  R iff a*b is

#### sMilips

##### New member
Q: Let S = {1,2,5,6 } Define a relation R on S of at least four order pairs, as (a,b)  R iff a*b is

Q: Let S = {1,2,5,6 }
Define a relation R on S of at least four order pairs, as (a,b)  R iff a*b is even (i.e. a multiply by b is even)

#### Olinguito

##### Well-known member
Re: Q: Let S = {1,2,5,6 } Define a relation R on S of at least four order pairs, as (a,b)  R iff a*

Hi sMilips .

You want $(a,b)$ such that $ab$ is even. So $(2,1)$ is possible since $2\cdot1=2$ is even. But you don’t want $(1,5)$ because $1\cdot5=5$ is odd. Thus $(1,5)\notin R$ but $(2,1)$ can be in $R$ (it doesn’t have to but you can include it if you want). In general, if $ab$ is even, what can you say about one (possibly both) of $a$ and $b$?

#### sMilips

##### New member
Re: Q: Let S = {1,2,5,6 } Define a relation R on S of at least four order pairs, as (a,b)  R iff a*