[多變] 94台聯 第四題
2 2
The maximum value of f(x,y)=y - x on the ellipse
2
x 2
--- + y =1 is ?
4
我本來想用lagrange解
但是求出兩個λ
-2x=λx/2 ->λ=-4
2y=λ2y ->λ=1
就不會解了...
2 2
所以我就想說那把 x =4-4y 代進f(x,y)
2
結果得出f =5y -4
一樣求不出max
請問這題要怎麼解?
謝謝
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