x=2 y=4-4a+ 1=5-4a
x = 4y = 16-8a+ 1 = 17-8a
x = y=a^2-2a^2+ 1=a^2+ 1
When a≤2 Ymin=5-4a Ymax= 17-8a
When a≥4 Ymin= 17-8a Ymax=5-4a.
When 2
When 3