若x=3的（m+1)次方,y=4－9的（2m－1）次方,用含x的代数式表示y,y=（）?

y=4-9^(2m-1)=>y=4-(3^3)^(2m-1)=>y=4-3^[3*(2m-1)]=>y=4-3^(6m-3)=>y=4-3^[(6m+6)-9]=>y=4-3^(6m+6)*3^(-9)=>y=4-[3^6*(m+1)]/(3^9)=>y=4-[3^(m+1)]^6/(3^9)=>y=4-x^6/(3^9)解毕.