aq1.9 imp

[Priyanshu Singh]

why is not 4th option injective

please explain

[Malabika Guha Mustafi]

Injective Function - 1.9 #5:) @ Guganesan , What is your opinion about the numerator part? Product of two x is square of x. On

[Debajyoti Biswas]

Priyanshu, checking injectivity is very easy.  The function f is said to be injective provided that for all a and b in X, whenever f(a) = f(b), then a = b; that is, f(a) = f(b) implies a = b.  Equivalently, if a ≠ b, then f(a) ≠ f(b). 

So basically if f(a)=f(b), does it lead to a=b only? If yes, then injective, otherwise not. 

[Satish]

Bro it is quadratic. It has two solutions, say x1 x2. That means f(x1)=f(x2) where x1 not equal to x2. So not one to one/injective.