若实数a.b满足ab-4a-b+1=o(a>1),求实数(a+1)*(b+2)的最小值
问题描述:
若实数a.b满足ab-4a-b+1=o(a>1),求实数(a+1)*(b+2)的最小值
答
解;由a>1可得a-1>0因为ab-4a-b+1=0(a>1)所以b=(4a-1)/(a-1)设f(a)=(a+1)(b+2)将b=(4a-1)/(a-1)代入可得f(a)=(a+1)(b+2)=(a+1)((4a-1)/(a-1)+2)=(6a-3)(a+1)/(a-1)=6(a-1)+[6/(a-1)]+15由于a-1>0所以...