[r]
Trang 1pHoNc coc.or viNu yrN HuoNG nAN cuAnn os rrurrl rRA HQc ri r .i
NAna Hoc: zotT - 2ot8
rvr6N: roAN o
r prrAnv tnAc Ncrrr$na: T6ng 3 di6m, mdi cau dfng dugo 0,5 di6m.
II.P IAN LUAN:
1 a t 2 te + 't9 L7z - 79.84:79(12+172-94;:79oo
(zu.s':z').zono
W
x - 10 :36 :4.3
x - l0:27 x:27 * l0
x:37
YQy x:37
= ( 2t.5').zo I 70 = 200.1 - 200
\L J ).Lv
L l
0,75
b
0,75
2
a
0,25
0,5
b (3., - 2u).7t :2.76
3.x - 2a :2.76:7s 3.x-24:14
3.x: 14 + 16
3.x:30
x:30:3
x: 10
VQyx:10
0,25
0,5
J
Gei s6 hgc sinh mOi O te
vi khi x6p hdng 10, hdng t2,himg l5 d6u thi6u 3 em n6n a + 3 chia h6t cho lO, 12 vd 15 Suy ra a + 3 e BC( 10,12,15)
l0 :2.5; 12:22,3; 15 : 3.5
BCNN( 10,12,15; : 22 3.5 : 60
a * 3e { 0O; 120;tB0;240;300;360; a2O; }
* a e {sl ;t t7 ;17 7 ;237 ;297 ;3 57 ; afi ; }
vi300(a{400n6n a:357
Vfy s6 hgc sinh t<trOi O cira trulng ld 357 em
0,25
0r5
0,5
0,25
Su,
d*
,!t
'
Trang 2a VE hinh dring, chinh x6c
TrOn tia Ot c6 OM < ON (2cm< 5cm) n6n di6m M nim gita hai
ili6m O vA N Ta c6:
OM + MN: ON
Me OM :2cm, ON: 5cm n6n 2 + MN: 5
MN:5-2:3cm
0,25
0,5 0,25
b
Vi di6m I ld trung di6m cta doqn th6ng OP n6n
or:oP 22 -!=2"*
LAp lu4n dusc di6m O nim gifia hai di6m M vd I (1)
Me OM :2cm, OI : 2cm n6n OM:OI (l)
Tt ( I ) vd (2) suy ra O li trung di6m cira doqn thing MI
,Ar?5
0,25
0r5
5
Ttr p : (n * 2).(r' * n - 5) suy ran -2vd n2 +
" -S ta uOc c.ia p.
Vi p ld s6 nguy6n t6 n6n n -2:1 hodc ,r' + ,, -5 :l
+ Niiu n -2:1 thi n : 3 Khi d6 p : l (3' + 3 -5) :7 lds6 nguy6n
t6( thOa mdn)
+N6urr'+n-5:l
n'+ n :6
n.(n+1):2.3
Suy ra n:2 Khi d6 p: (2 * 2).1: 0 kh6ng ld s6 nguy6n t6
v4yn:3
0,25
0,25
chfi i,:
- HQc sinh gi6i c6ch kh6c, n6u dirng v6n cho di6m t6i da.
- Hgc sinh kh6ng vE hinh hodc vE hinh sai thi kh6ng chdm bdi hinh .r, ,
.':
,