3的X次方等于4,3的Y 次方等于6 3^x=4,3^y=6 9的2X-Y次方加27的X-Y次方 =(3^2)^(2x-y)+(3^3)^(x-y) =3^(4x-2y)+3^(3x-3y) =[(3^x)^4]/[(3^y)^2]+[(3^x)^3]/[(3^y)^3] =4^4/6^2+4^3/6^3 =256/36+64/216 =64/9+8/27 =19...