第17题怎么做😊
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y=f(x²+y²)+f(x+y)
dy/dx=y'=f'(x²+y²)(2x+2yy')+f'(x+y)(1+y')
y'=[2x·f'(x²+y²)+f'(x+y)]/[1-f'(x+y)-2yf'(x²+y²)]
x=0,y=2,f'(2)=5,f'(4)=¼代入,得
dy/dx|x=0 =[2·0·f'(0²+2²)+f'(0+2)]/[1-f'(0+2)-2·2·f'(0²+2²)]
=f'(2)/[1-f'(2)-4·f'(4)]
=5/(1-5-4·¼)
=-1
dy/dx=y'=f'(x²+y²)(2x+2yy')+f'(x+y)(1+y')
y'=[2x·f'(x²+y²)+f'(x+y)]/[1-f'(x+y)-2yf'(x²+y²)]
x=0,y=2,f'(2)=5,f'(4)=¼代入,得
dy/dx|x=0 =[2·0·f'(0²+2²)+f'(0+2)]/[1-f'(0+2)-2·2·f'(0²+2²)]
=f'(2)/[1-f'(2)-4·f'(4)]
=5/(1-5-4·¼)
=-1
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