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![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
a: Thay x=0 và y=5 vào (d), ta được:
m*0+5=5
=>5=5(đúng)
=>ĐPCM
b: x1<x2; |x1|>|x2|
=>x1*x2<0
PTHĐGĐ là:
x^2-mx-5=0
Vì a*c<0
nên x1,x2 luôn trái dấu
=>Với mọi m
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có: \(\frac{2003.2004}{2003.2004}=1\)
1+1=2
Vậy \(\frac{2003.2004}{2003.2004}\)+1 > \(\frac{2004}{2005}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 2:
mCuSO4(tổng) = 200.10%+300.20%=80(g)
mddCuSO4(sau) = 200+ 300=500(g)
=> C%ddCuSO4(Sau)= (80/500).100=16%
Bài 1:
nNaCl(tổng)= 3.0,2+2.0,4= 1,4(mol)
VddNaCl(Sau)= 3+2=5(l)
=>CMddNaCl(Sau)= 1,4/5=0,28(M)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
2 The meeting will be held before May Day
3 The engine of the car has to be repaired
4 A story is going to be told by the teacher
5 The cake is being cut with a sharp knife by Mary
6 Luckily for me, my name wasn't called
7 His story isn't believed
8 After class, the chalk board is always erased by one of the students
9 The victims have been provided with food and drink
11 Each of us were given 2 exercises books
12 He will be told that news
13 A lot of money was paid me to do the job
14 The window of the laboratory has been changed
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
25. cleverer nhé (of the 2_ 27. C 29. C (help someone to do/ do sth) 30. D
are saving-are going to buy
listening - reading
are sleeping
makes
will not rain
does not go
to travel
laughing
less => fewer
lately=> late
does it cost => it costs
are => is
four-hours => four-hour
proud
actress
older
II
a)are saving/will buy
b) listening/reading
c)are sleeping
d)makes
e)won't rain
f) isn't going
g)to travel
h)laughing
![](https://rs.olm.vn/images/avt/0.png?1311)
+) Nếu a>0 khi đó VT>225 (với mọi b là số tự nhiên) => MT
=>a=0
=> (3b+1)(b+1)=225
=> tìm đc b
Câu 7
\(A.x^{12}\)
Câu 8
\(D.\frac{7}{25}\)