x²-8x+16+4y²=4
(x-4)²/4+y²=1
令y=sina
(x-4)²/4=1-sn²a=cos²a
(x-4)/2=cosa
x=2cosa+4
x²+y²
=4cos²a+16cosa+16+sin²a
=3cos²a+16cosa+17
=3(cosa+8/3)²-13/3
-1
x²-8x+16+4y²=4
(x-4)²/4+y²=1
令y=sina
(x-4)²/4=1-sn²a=cos²a
(x-4)/2=cosa
x=2cosa+4
x²+y²
=4cos²a+16cosa+16+sin²a
=3cos²a+16cosa+17
=3(cosa+8/3)²-13/3
-1