中三-四邊形[20點]

6) BC = DC
2x+1 = 8
2x = 8-1
x = (8-1)/2
x = 3.5

AB = AD
<ABD = <ADB = y
<50 + <ADB + <ABD = <180
<50 + y + <ABD = <180
y = (<180 - <50)/2
y = <65

7) <HEF = <HGF
<HEF = 2x - <10
<HEF + < EFG = <180

<140 - 3x = 2x - <10 <HEF + < EFG = <180
<140 + <10 = 2x + 3x 2x - <10 + 4y = <180
<150 = 5x 2(<30) - <10 + 4y = <180
<30 = x <60 - <10 + 4y = <180
<50 + 4y = <180
4y = <180 - <50
4y = <130
y = <32.5