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) 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) | 
