satOG第三版p90612p9081912.ifyisdirectlyproportionaltox^2andy=1/8whenx=1/2,whatisthepositivevalueofxwheny=9/2?19.thecostofmaintenanceofanautomobileincreaseseachyearby10percent,andAndrewpaid300thisyearform

Question

sat OG 第三版 p906 12 p908 19
12.if y is directly proportional to x^2 and y=1/8 when x= 1/2,what is the positive value of x when y=9/2?
19.the cost of maintenance of an automobile increases each year by 10 percent,and Andrew paid 300 this year for maintenance on his automobile.If the cost c for maintenance on Andrew's automobile n years from now is given by the function c(n)=300x^n,what is the value of

Answer 1

12.得三
x方得四分之一,y跟他成正比例,那就是y=0.5x方,再代入,就得了
19车保养费一年涨十分之一,今年三百,公式是上述的,问x,就是每年maintenance 费用是上年的几倍,答案是1.1