Question

When f(x)=4 what is the value of x?

Answer 1

From the mapping above it can be seen that the given relationship is bijective (one-to-one and onto or one-to-one correspondence) as each element of the range is mapped to by exactly one element of the domain. So f(x)=4 implies f(2)=4 or simply x=2

Answer 2

When f(x) = 4 then x = 2 (domain = 2, range = 4)

hope it helps