The domain is the range of xx values which give f(x)f(x) a value that is unique, such there is only one yy value per xx value.
Here, since the xx is on the bottom of the fraction, it cannot have any value such that the whole denominator equals zero, i.e. d(x)!=0d(x)≠0 d(x)=text(denominator of the fraction that is a function of)d(x)=denominator of the fraction that is a function of xx.
x-2!=0x−2≠0
x!=2x≠2
Now, the range is the set of yy values given for when f(x)f(x) is defined. To find any yy values that cannot be reached, i.e. holes, asymptotes, etc. We rearrange to make xx the subject.
y=5/(x-2)y=5x−2
x=5/y+2x=5y+2, y!=0y≠0 since this would be undefined, and so there are no values of xx where f(x)=0f(x)=0. Therefore the range is f(x)!=0f(x)≠0.