Hello
Malarvizhi, one of the easiest ways to check if a function is bijective is to see whether the codomain = range of the given function. In case you don't know the codomain, please note it is always the the second part of the defintion. So here the defintion says the function is defined from R to R so the codomain here would be the second part i.e R.
Because of the modulus function you will always get a positive value as output. Hence the codomain is not equal to the range and so the given function is not bijective.
Hope it helps.
