∵3^x=4,3^y=6
∴3^(x-y)=3^x/3^y=4/6=2/3
∴9^(x-y)+27^(x-y)=[3^(x-y)]²+[3^(x-y)]³
=(2/3)²+(2/3)³
=4/9+8/27
=20/27
已知3^x=4,3^y=6求9^x-y+27^x-y的值
∵3^x=4,3^y=6
∴3^(x-y)=3^x/3^y=4/6=2/3
∴9^(x-y)+27^(x-y)=[3^(x-y)]²+[3^(x-y)]³
=(2/3)²+(2/3)³
=4/9+8/27
=20/27