※ 引述《haby (haby)》之铭言： : 63. : For which of the following functions is f(a + b) = f(a) + f(b) for all : positive numbers a and b ? : (A) f(x) = x^2 : (B) f(x) = x + 1 : (C) f(x) = 根号2 : (D) f(x) = 2/x : (E) f(x) = -3x : 答案E 这种类的题目要怎麽解呢@@~~ 这个题目用代的好了 题目说 f(a+b)=f(a)+f(b) A.f(a+b)=(a+b)^2=a^2+b^2+2ab f(a)=a^2,f(b)=b^2 不选 差了2ab这项 B.f(a+b)=a+b+1 f(a)=a+1,f(b)=b+1 不选 差1 C.不管什麽都是根号2 相加会变成 2跟号2 不选 D.f(a+b)=2/(a+b) f(a)+f(b)=2/a+2/b=(2a+2b)/ab E.f(a+b)=-3(a+b) f(a)+f(b)=(-3a)+(-3b) 选E : 64. : Are at least 10 percent of the people in Country X who are 65 years old or : older employed? : (1) In Country X, 11.3 percent of the population is 65 years old or older. : (2) In Country X, of the population 65 years old or older, 20 percent of the : men and 10 percent of the women are employed. : 答案B 题目问是不是至少有10%的人口是 65岁以上(含)有工作的 (1)不知道工作 (2)在65岁以上(含) 有20%m,10%f是有工作的 题目问的是有没有大於等於10%(f+m) 可以算选Bꔊ : 180. : Are x and y both positive? : (1)2X-2Y=1 : (2)X/Y>1 : 答案C (1)2(x-y)=1 (2) 考虑正负关系 若y>0 则x>y 若y<0 则x<y(乘负号 不等式换方向) 合并 y>0 代入(1) 2(x-y)=1 两个都是正数 y<0 代入(1) 不合 x<y 因为2(x-y)=1 会小於0 选c : 192. : Of the 75 houses in a certain community, 48 have a patio. How many of the : houses in the community have a swimming pool? : (1) 38 of the houses in the community have a patio but do not have a swimming : pool. : (2) The number of houses in the community that have a patio and a swimming pool : is equal to the number of houses in the community that have neither a : swimming pool nor a patio. : 答案B 我选C 囧> 要怎麽只看第二个选项推得呢?? (2)两个都有=两个都没有 设为N 原题问S多少 P+S-N+N=75 S=27 (题目是说这75间房子 P有48,S不知 但也有两个同时有的 或两个同时没有的) 所以得到上面式子 画图也行 选B : 198. : Did one of the 3 members of a certain team sell at least 2 raffle tickets : yesterday? : (1) The 3 members sold a total of 6 raffle tickets yesterday. : (2) No 2 of the members sold the same number of raffle tickets yesterday. : 答案D 恩恩 不太懂第二个选项@@~~ : 麻烦好心人解答 感恩^^ (1)全部卖出6 一定会有大於2的 (2)没有任何两人是卖相同数目的 也就是说 假设有一个卖0 其他两个卖1,2 这是最小可能 选D --

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