In case(a) step no.3 , instead of taking x-1 can't we take x-3 or x+1 given in above step ?and the intervals will be different. If not then explain with reason.

In case(a) step no.3 , instead of taking x-1 can't we take x-3 or x+1 given in above step ?and the intervals will be different. If not then explain with reason. (a) f(x) is increasing (x-1)20 x ell, . f(x) is increasing on (1, Ifrom