The function f is defined for each positive three-digit integer n by f(n)=2x3y5z, where x, y and z are the hundreds, tens, and units digits of n, respectively. If m and v are three-digit integers such that f(m)=9f(v), then m-v=?
求助各位nn丫~~想不到用什么办法来做额。。。
here is my opinion
f(m)= 2^x * 3^y * 5^z
f(v)= 2^x' * 3^y' * 5^z'
=2^(x-x')* 3^(y-y') * 5^ (z-z')=9
so x-x'=0, z-z'=0, y-y'=2
y is the tenth digit of the three digit number. y-y'=2 is the tenth digit of the number (m-v)
x-x'=0 is the hunderd digit, and z-z' is the unit.
so m-v=20
嗯 就是这个答案~~ 太强悍啦~~
万分感谢吖~~~
厉害了~~
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