Let sin2x=t, because the range of sin2x is [- 1, 1], so the range of t is [- 1, 1].

So y=7-2t+t? ，t in [- 1， 1]

y=7-2t+t？ =(t- 1)？ +6

So when t=- 1, the maximum value of the function is 10.

When t= 1, the minimum value of the function is 6.