x2+4y2=4x
x²-4x+4y²=0
(x-2)²+4y²=4
0≤x≤4
-1≤y≤1
x2+4y2=4x得y²=(4x-x²)/4
x²-y²
=x²-(4x-x²)/4
=5x²/4-x
=(5/4)(x²-4x/5)
=(5/4)(x-2/5)²-1/5
當(dāng)x=2/5時(shí),x²-y²有最小值為-1/5
當(dāng)x=4時(shí),x²-y²有最大值為160≤x≤4 -1≤y≤1怎么得出的因?yàn)槠椒街刀际谴笥诘扔诹?x-2)²+4y²=44y²≥0，所以(x-2)²≤4，可得0≤x≤4(x-2)²≥0，所以4y²≤4，可得-1≤y≤1