PP3数学4题目---不懂

liming21

Quantity:
1, the rate of a certain chemical reaction is directly proportional to the square of the concentration of chemical A present and inversely proportional to the concentration of chemical B present. If the concentration of chemical B is increased by 100 percent, which of the following is closest to the percent change in the concentration of chemical A required to keep the reation rate unchanged?
50% decrease
40% decrease
40% Increase
50% increase

都没看懂,...

(2)
If X^4 +y^4=100, the the greatest possible value of x is between

0 and 3
3 and 6
6 and 9

答案:3 and 6!!!太奇怪了,我觉得是0 and 3

(3)
If xy=1, what is the value of 2(x+y)^2/2(x-y)^2

答案16

(4) If x>y^2>z^4, which of the following statements could be true?
1, x>y>z
2, z>y>x
3, x>z>y

a 1 only
b 1and 2 only
c 1and 3 only
d 1 and 2 and 3

tokugawa

1.某化学反应速度与A物质浓度平方成正比，与B物质浓度成反比，那么B浓度扩大1倍，化学反应速度不变，那么A扩大多少？

因为B扩大一倍，所以A平方扩大1倍，1.4*1.4=1.96， 所以应该试40%

2.X=0的时候Y最大，这时候Y是在3--6间，题目没说XY试整数

3.估计题目有误

4.第一个可以： X=10 Y=2 Z=1 第二个可以：X=0.6 Y=0.7 Z=0.8 第三个可以： X=10 Y=-2 Z=1

liming21

thanks