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3求a,b的值,使点(13)是曲线y=x3+ax2+b的拐点?
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咨询记录 · 回答于2022-06-14
3求a,b的值,使点(13)是曲线y=x3+ax2+b的拐点?
y=x3+ax2+b的拐点?3=a×1^3+b×1^2a+b=3b=3-ay=ax^3+(3-a)x^2y'=3ax^2+2(3-a)x=3ax^2+(6-2a)xy"=6ax+6-2a=2(3ax+3-a)y"=02(3ax+3-a)=03ax+3-a=03ax=a-3x=1/3-1/a∵P(1,3)是拐点∴x=11/3-1/a=11/3-1=1/a-2/3=1/aa=-3/2b=3-a=3-(-3/2)=3+3/2=9/2