数学选择题我算的对不对?那9题呢?
来源:学生作业帮 编辑:搜搜做题作业网作业帮 分类:数学作业 时间:2024/07/10 19:02:58
数学选择题我算的对不对?那9题呢?
7题 C
8题 A
9题 A 对吧?
![数学选择题我算的对不对?那9题呢?](/uploads/image/z/5320020-12-0.jpg?t=%E6%95%B0%E5%AD%A6%E9%80%89%E6%8B%A9%E9%A2%98%E6%88%91%E7%AE%97%E7%9A%84%E5%AF%B9%E4%B8%8D%E5%AF%B9%3F%E9%82%A39%E9%A2%98%E5%91%A2%3F)
9T 过程1/x-1/y=3
y/xy-x/xy=3
(y-x)/xy=3
y-x=3xy
x-y=-3xy
5x+xy-5y/x-xy-y
=5(x-y)+xy/(x-y)-xy
=-15xy+xy/-3xy-xy
=-14xy/-4xy
=7/2
7.8 T都对了 !
y/xy-x/xy=3
(y-x)/xy=3
y-x=3xy
x-y=-3xy
5x+xy-5y/x-xy-y
=5(x-y)+xy/(x-y)-xy
=-15xy+xy/-3xy-xy
=-14xy/-4xy
=7/2
7.8 T都对了 !