35.
1) AC = 3BC
BC = AC - AB = 3BC - AB
BC = AB/2 = 3/2 = 1.5(cm)
DC = AD + AB + BC = AB/2 + AB + AB/2 = 2AB = 2*3 = 6(cm)
2) AK = BK; DK = AD + AK = AB = BK + BC = CK 所以,K是AB和CD的中点
31,
1) (x+1)/5 - x = (1-x)/2
两边同乘以10得
2x + 2 - 10x = 5 - 5x
-3x = 3
x = -1
2)(2-x)/2 - (x+2)/6 = 2/3
两边同乘以6得
6 - 3x - x - 2 = 4
-4x = 0
x = 0
32.
1)
3AC = 2AB
AC/2 = AB/3
DE = DB - BE = AB/2 - BC/2 = AB/2 - (AB - AC)/2 = AB/2 - AB/2 + AC/2 = AC/2 = AB/3 = 6
AB = 18
2)
CB = AB - AC = AB - 2AB/3 = AB/3
AD:CB = (AB/2):(AB/3) = 3:2
35.(1).BC 1.5cm;DC 6cm
(2).AB,CD
31.(1).x=-1 (2).x=0
32.(1).36 (2).3:2
解析公式 这个很简单的啊 别着急 慢慢理清思路就好了 真的 不难
(1)(x+1)/5-x=(1-x)/2
2(x+1)-10x=5(1-x)
2x+2-10x=5-5x
2x-10x+5x=5-2
-3x=3
x=-1
(2)(2-x)/2-(x+2)/6=2/3
3(2-x)-(x+2)=4
6-3x-x-2=4
-3x-x=4-6+2
-4x=0
x=0