sin^2 x+cos^2 x=(sinx+cosx)^2-2sinxcosx=1因为sinx,cosx为方程两个根∴sinx+cosx=-b/a=-3m/4sinxcosx=b/a=2m+1/8∴9m^2/16 -4m+2/8=19m^2-8m-4=169m^2-8m-20=0m - 29m 10(m-2)(9m+10)=0m=2或m-10/9（舍）∴m=2...9m^2-8m-4=16 9m^2-8m-20=0是什么意思？移项