1.A relation R is defined on the set Z of integers as follows:

(x,y)∈R iff x ² + y ² = 25.

Express R and R-1 as the set of odered pairsand hence find the respective domains.

2.Letf : R → R . be defined as { 2x+1, x<= 4 Show that f is not a function

x+1 , x>=4 }

Dear Student! 

 Here is the link for the answer to your query.

(1) https://www.meritnation.com/ask-answer/question/1-a-relation-r-is-defined-on-the-set-z-of-integers-as-follo/relations-and-functions/2674986

(2) At x = 4, f(x) can have both values 2x + 1 and x + 1.

2(4) + 1 = 9

and 4 + 1 = 5

So,  f(x) has two images for the value x = 4.

But a function cannot have more than two images for a particular domain value, hence f(x) is not a function.