Question

若f(x)=a㏑x+bx²+x在x=1和x=2处取得极值,则a=?,b=?

Answer 1

f′(x)=a/x+2bx+1;

f′(1)=a+2b+1=0;

f′(2)=a/2+4b+1=0;

a+8b+2=0;

6b+1=0;

b=-1/6;

a=-2/3;

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