Q.Find the possible domains for which the following are one to one functions

a) y = x^2

b) y= x(x-2)

c) y = 2x-3

i kno the for a 1-1 function there is max and min of the 1 y-value for every x-value and vice-versa

all i need is now are the answers and the explanations to the answers.

for eg i for b) i know that domain: x<=0 or x>=1 but why not x<=0 or x>=2

i am so damn confused, please help me thank you