Find the increasing interval of function y = - (x-3) &; | x | I don't know how to remove the sign of absolute value and divide it into several conditions

Find the increasing interval of function y = - (x-3) &; | x | I don't know how to remove the sign of absolute value and divide it into several conditions

In general, if there is an absolute value, we only need to discuss the positive and negative of the function in the absolute value
The above question can be like this
(1) When x > 0, y = - x (x-3)
(2) When = 0, y = 0
(3)x

Find that y = x ^ 2-2 [x] - 3 is the absolute value sign

In addition to discussing the positive and negative methods of X, we can also do this
y=[x]^2-2[x]-3
=([x]-3)([x]+1)