Tolong dijawab nomor 3&4 yaa:) sama tolong dicek nomor 1&2 sudah bener ato blom:) makasih!!

Bab Garis dan Sudut
Matematika SMP Kelas VII


nomor 3
DP/DA = DQ/DC
3/5 = DQ/DC
3/5 = (DC-QC)/DC
3/5 = DC/DC - QC/DC
3/5 = 1 - QC/DC
QC/DC = 1 - 3/5
QC/DC = 2/5

CR/CB = CQ/CD
5/CB = 2/5
2.CB = 5.5 = 25
CB = 25/2 = 12,5 cm
dengan demikian
RB = CB - CR = 12,5 - 5 = 7,5 cm
Jadi panjang RB adalah 7,5 cm


misal : QR=SB=x (segi empat QRSB adalah jajar genjang)
QR/DB = CQ/CD
QR/(DS+SB) = CQ/CD
x/(4+x) = 2/5
5x = 2(4+x)
5x = 8 + 2x
5x - 2x = 8
3x = 8
x = 8/3 = 2⅔
jadi panjang SB = 2⅔ cm

nomor 4
CS/CD = CR/CO
3/8 = CR/CO
3/8 = (CO-OR)/CO
3/8 = CO/CO - OR/CO
3/8 = 1 - OR/CO
OR/CO = 1 - 3/8
OR/CO = 5/8

QO/OB = OR/CO
QO/6 = 5/8
8.QO = 6.5 = 30
QO = 30/8
QO = 3¾ cm
Jadi panjang QO adalah 3¾ cm

BQ = OB - QO
BQ = 6 - 3¾
BQ = 2¼ cm
Jadi panjang BQ adalah 2¼ cm

OP/OA = QO/OB
OP/(OP+AP) = QO/OB
OP/(OP+2) = 5/8
8.OP = 5.(OP+2)
8OP = 5OP+10
8OP - 5OP = 10
3OP = 10
OP = 10/3
OP = 3⅓

Jadi panjang OP = 3⅓ cm