If y = x2 - 6x + 9, what is the value of x ?
(1) y = 0
(2) x + y = 3
Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient.
题目分析:
题目给定的函数为~$y=x^2-6x+9=(x-3)^2$~。
(1) 如果y=0,~$y=x^2-6x+9=(x-3)^2=0$~,则解得x=3,题目得解。
(2) 如果x+y=3,则y=3-x,代入题目中的式子得到,~$3-x=(x-3)^2$~,只根据此式,则x可能为3,也可能为1,均满足条件2,所以,无法根据条件2确定x的值。
因此,本题答案为(A),仅条件1可以解题,条件2不行。
DS 有解必须满足唯一性
注意(x-3)^2=0的解,有且只有一个
条件二得出来的两个值应该分别为3和2吧,解析写错了
不可能是1的 朋友
2为什么错呢?难道因为可以得出两个x,所以就错吗?即答案不唯一,就为错。
可能因为what is the value of x 而不是 values 吧?
OG的DS里说明过:In Data Sufficiency problems that ask for the value of a quantity, the data given in the statements are sufficient only when it is possible to determine exactly one numerical value for the quantity
厉害了
多谢提醒
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