Get-5π/4+2kπ

Therefore, the increasing interval of the function is [-5π/4+2kπ, -π/4+2kπ], k ∈ z.

(2)y= -sin(2x-π/4)，

Through 2kπ-π/2

kπ-π/8 & lt； = x & lt=kπ+3π/8，k∈Z，

Therefore, the decreasing range of the function is [kπ-π/8, kπ+3π/8], k ∈ z.