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 > \(\frac{2004}{2005}\)

TL: dấu này >

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)

= 2 833 273 065 097 235 810

= 2 833 273 065 097 235 810

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

C

C

B

A

C

A

cảm ơn nhiều

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

bạn cho mình hỏi b=bao nhieu