3/0.75=300/75=4:15/11:7/11=5:71/12:1/15=5:48/9:8/13=13:90.15:0.12=5:40.7:21=1:375/100=3:4望采纳…………不懂可问我

题目[1]3.2;16是 1:5 题目[2]1.85;0.75是 37:15 题目[3]3小时;45分钟是 4:1

X-1- 8 / (X+1)=(x-1)-8/(x+1) =(x-1)(x+1)/(x+1)-8/(x+1) =(x^2-1^2)/(x+1)- 8/(x+1) =(x^2-1-8)/(x+1) =(x^2-9)/(x+1) =(x+3)(x-3)/(x+1)

方法:递推法记所求行列式为dn最后一行拆分为:0 0 0 ……1 和 ana1 ana2 ana3 …. -a(n-1)加到第一行,第二行,第三行,……,第n-1行,化成一个n阶下三角行列式,.