i'm working on 4 and 5, give me a sec
1 If a and b are positive and 7a-5=2. what is the greatest possible value of ab. 为什么是10而不是2?
求的是最大值, 由第一个公式得出a=5, 两者相乘最大值是2×5=10.
2 If n is an integer, then the units digit of CANNOT be _?
A 0 B 2 C 4 D 5 E 6 why choose B?
如果n是整数,那么——【你有个公式没写出来吧?】的个位数不能是什么.看你题目的答案,是n^2吧? 没有任何数的平方是2结尾. 2的平方是4,5的平方是25,6的平方是36
3 The product of two consecutive positive integers CANNOT be__?
A a prime number B divisible by 11 C a multiple of 13 D an even number less than 10 E a number having 4 as its units digit Why choose E ? I cannot understand the meaning of E?
两个相邻的正数之积不能是?
素数 【可以,1乘2】
被11整除 【可以,11乘12】
13的倍数 【可以,12乘13】
一个小于10的偶数 【可以,2乘3】
个位数结尾是4. 【其他都可以,所以这个不可以】
4 The daily rate for hotel room that sleeos 4 proplr is $39 for one person and X dollar for each additional person. If 3 people take the room for one day and each pays $21, what is the value of X? Why the answer is 12 rather than 8?
三个人一共付款63元21*3 = 63
一个人的话是39元,所以多出来的两个人本身的价格是63-39=24,
所以每多出一个人是24÷2=12元
5 If r and s are positive integers, each greter than 1, and if 11(s-1)=13(r-1), what is the least possible value of r+s? Why the answer is 26 rather than 2?