3^x=4,9^y=7,3x-2y=()
问题描述:
3^x=4,9^y=7,3x-2y=()
答
3^x=4,
x=log3 4
9^y=7,
3^2y=7
2y=log3 7
3x-2y
=3log3 4-log3 7
=log3 (64/7)