Find the domain of the following relation:
={(13,45),(15,51),(17,57),(19,63)}

The beginning time of relay race is 6.73 minutes

Step-by-step explanation:

Given as :

The final time of relay race = 3.96 minutes

Let The initial time of relay race = x minutes

At first, The time reduce by 2.1 min

So, The first time become = ( x - 2.1 ) min

At second , The time reduce by = 0.1

So, The time become =  ( x - 2.1 ) min - min

Or,  

∵ final time of race = 3.96 min

∴ = 3.96

Or, 9 x - 21 = 3.96 × 10

Or, 9 x = 39.6 + 21

Or, 9 x = 60.6

∴  x =

i.e  x = 6.73 minutes

So, The beginning time = x = 6.73 min

Hence,The beginning time of relay race is 6.73 minutes Answer