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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
Ta có: \(\frac{2003.2004}{2003.2004}=1\)
1+1=2
Vậy \(\frac{2003.2004}{2003.2004}\)+1 > \(\frac{2004}{2005}\)
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)
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
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
+) 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
She learns graphs ,equations and calculations in math.
You learn how to sing and play the piano in music.
Lan learns past events in VN and around the world.
có gì sai thì sua hộ mình nhé !
o câu cuối thiếu "in history" ,thêm vào hộ mình nhé !