DKXD r6i rirt gon bir5u thirc.[r]
Trang 1PFIONG GIAO DUC VA DAO TAO KHAO SAT CUAT LUONG CUOI
D6 chinh thri'c D€ m6n: To6n hoc lop 8
Thdi gian: 90 phf t (kh6ng k€ thdi gian giao c16)
C6u 1 (1,5 di6m) Cho bi6u thfrc P =[ !-:J-I tt
-+-
|
a) Tim DKXD r6i rirt gon bir5u thirc P
b) Tim circ gi|tri nguyen cria x ee p nnan gi|tri nguy6n
CAu2 (2,5 di€m) Giai c6c phucnrg trinh vd b6t phuong trinh sau:
b) 3+ 2(x+5)<s
,1I2x-3
,1 I _
Ciu 3 (2,0 di6m)
M6t nguoi di xe m6y tuA d6n B v6i vpn t6c 30 kmih D6n B ngudi d6 ldm viQc
trong 1 gio rdi quay tro vd A v6i vdn t6c 24 iylnr/h T6ng thoi gian tir hic
"u6t ph6t cho tdi khi vO d6n A ld 5 gid 30 phut Tfnh qudng ducrng AB?
Cdu 4 (3,5 ii6m )
Cho tam gi6c nhon ABC, c6 cttc duong cao AD, BE, CF cit nhau tai H
a) Chirng minh ring tam gi6c ADC d6ng dang vdi tam gi6c BEC
b) Chung minh ring BH.HE - CH.HF
c) Chung minh ,ing !2*Y*!-L=l
Ciu 5 (0,5 di6m)
Cho a >0,b>0 tho6 mdn a+b31 Tim giittrinh6nhAtcriabi6uthirc:
,7)
A= . -:t - t4Ab
a'+b' ab
Lwu y: Gido vi€n coi khdo sdt kh6ng giai th{ch gi thAm.