1.已知实数a,b满足ab=1,则1/(a²+1)+1/(b²+1)= 2.若1/x+2/y+3/z=5,3/x+2/y+1/z=7,则1/x+1/y+1/z=
问题描述:
1.已知实数a,b满足ab=1,则1/(a²+1)+1/(b²+1)= 2.若1/x+2/y+3/z=5,3/x+2/y+1/z=7,则1/x+1/y+1/z=
答
1/(a²+1) + 1/(b²+1)=[(b²+1)+(a²+1)]/[(a²+1)(b²+1)]=(b²+a²+2)/(b²+a²+1+a²b²)=(b²+a²+2)/(b²+a²+2)=2化简得y=x/(4x-2)z=x/(1-...