[求助]这两题看不明白，请教高人！

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

Key 3

2,The rate of a certain chemical reaction is directly proportional to the square of the concentration of chemical A present and inversly proportional to the concentration of chemical B present. If the concentration of chemical B is increased by 100%,which of the following is of chemical A required to keep the reaction rate unchanged?

Key 40% increase

请教两道题目，我不知道怎么做，谢谢大家啦！！！