解log81(X)+log9(X)+log3(X) < 7/4
log81(X)+log9(X)+log3(X) < 7/4
log3^4(x)+log3^2(x)+log3(x)<7/4
1/4log3(x)+1/2 log3(x)+ log3(x)<7/4
7/4 log3(x)<7/4
log3(x)<1
0<x<3
log81(X)+log9(X)+log3(X) < 7/4
log3^4(x)+log3^2(x)+log3(x)<7/4
1/4log3(x)+1/2 log3(x)+ log3(x)<7/4
7/4 log3(x)<7/4
log3(x)<1
0<x<3