若2s^2+13s+1=0,2t^2+13t+1=0,则s+t=
问题描述：
若2s^2+13s+1=0,2t^2+13t+1=0,则s+t=
答
2s^2+13s+1=0,
2t^2+13t+1=0
2(s^2-t^2)+13(s-t)=0
=>2(s+t)(s-t)+13(s-t)=0
=>(2(s+t)-13)(s-t)=0
若s不等于t,那么有2(s+t)-13=0
=>s+t=13/2