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laca

1. XY+Z=X(Y+Z)

Answer: X=1 or Z=0

But I chose X=1 and Y=1

不是也可以吗?

2.For a finite sequence of nonzero numbers, the number of variations in  sign is defined as the number of pairs of consecutive terms of the two sequence for which the product of the two consecutive terms is negative. What is the number of variations is in sign for the sequence.  1, -3, 2, 5, -4, -6

Answer:3個

3. For which of the following function f is f(x)=f(1-x)

Answer: f(x)=x^2(1-x)^2

请大家帮帮忙!谢谢

Youknowme

以下是引用laca在2006-1-9 18:45:00的发言：

1. XY+Z=X(Y+Z)

Answer: X=1 or Z=0

But I chose X=1 and Y=1

不是也可以吗?

澧:楼主考虑的不全面.依楼主如果只考虑X为1的情况等式是可以成立的,但是如果仅考虑Y为1等式是不成立的,当Y=1时,等式为X+Z=X(1+Z),显然不成立,实际上还有一种情况Z为0则没有考虑

spread

以下是引用laca在2006-1-9 18:45:00的发言：

1. XY+Z=X(Y+Z)

Answer: X=1 or Z=0

But I chose X=1 and Y=1

不是也可以吗?

According to what you've provided, I think your answer should be right.

2.For a finite sequence of nonzero numbers, the number of variations in  sign is defined as the number of pairs of consecutive terms of the two sequence for which the product of the two consecutive terms is negative. What is the number of variations is in sign for the sequence.  1, -3, 2, 5, -4, -6

Answer:3個

I'm not sure about the where does the 'highlighted' two come from.

My understanding is that, the question asks you how many pairs of consecutive terms in the sequence have a negative product.

In the sequence shown, there are three pairs.

Namely, 1&(-3), (-3)&2, 5&(-4)

3. For which of the following function f is f(x)=f(1-x)

Answer: f(x)=x^2(1-x)^2

请大家帮帮忙!谢谢

f(1-x)=(1-x)^2*[1-(1-x)]^2=(1-x)^2*x^2=f(x)

[此贴子已经被作者于2006-1-9 22:16:59编辑过]

beautifulmind

X=1 and Y=1是X=1 or Z=0的子集，所以后者

lemony55

f(1-x)=(1-x)^2*[1-(1-x)]^2=(1-x)^2*x^2=f(x) 看不懂啊！

dianecarton

以下是引用laca在2006-1-9 18:45:00的发言：

1. XY+Z=X(Y+Z)

Answer: X=1 or Z=0

But I chose X=1 and Y=1

不是也可以吗?

2.For a finite sequence of nonzero numbers, the number of variations in  sign is defined as the number of pairs of consecutive terms of the two sequence for which the product of the two consecutive terms is negative. What is the number of variations is in sign for the sequence.  1, -3, 2, 5, -4, -6

Answer:3個

3. For which of the following function f is f(x)=f(1-x)

Answer: f(x)=x^2(1-x)^2

请大家帮帮忙!谢谢

请大家帮帮忙!谢谢

第一题，楼主选的答案包含于X=1 or Z=0之中

第二题，楼主应该大错了个地方，就是sequence前面没two,这题是问相邻两数乘积为负的有几对。选3

第三题，把1-x代入f(x)=x^2(1-x)^2

f(1-x)=(1-x)^2*x^2=x^2(1-x)^2=f(x)满足f(x)=f(1-x)

小小天

还是不明白第二题目啊 ～～～～救救我啊 谁
我把那6个数字在数轴上写好 只能是 -3和1才是负数啊？ 怎么会有三对 他必须是连续的数啊 就必须在数轴上啊 相邻的能变成负数的只有-3和1啊
-6 -4 -3 1 2 5

pheobe

不要把那个sequence按照大小排列

题目中给出的不仅是terms,terms的顺序也是固定的,不能改的

consecutive表示的是sequence中的相临数字

玻璃青橙

第二题啥意思,能不能翻译一下?

auflute

第二题

对于一个有限的数列，该数列中相邻两项乘积为负的有几对，把对数定义为变量的数量。