giúp mình vs,mình đang gấp lắm ahhh
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\(\Delta'=m^2-\left(m^2-1\right)=1>0\)
vậy pt có nghiệm pb x1;x2
Theo Vi et \(\left\{{}\begin{matrix}x_1+x_2=2m\left(1\right)\\x_1x_2=m^2-1\left(2\right)\end{matrix}\right.\)
Ta có : \(x_1+2x_2=7\left(3\right)\)
Từ (1) ; (3) ta có hệ \(\left\{{}\begin{matrix}x_1+x_2=2m\\x_1+2x_2=7\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x_2=7-2m\\x_1=2m-7+2m=4m-7\end{matrix}\right.\)
Thay vào (2) ta được
\(\left(7-2m\right)\left(4m-7\right)=m^2-1\Leftrightarrow28m-49+8m^2+14=m^2-1\)
\(\Leftrightarrow7m^2+28m-34=0\Leftrightarrow m=1;m=-\dfrac{34}{7}\)
I
1 A
2C
3 B
4 D
5 B
II
1 D
2 B
3 B
4 B
5 A
6 D
7 B
8 B
9 D
10 A
III
1 leaving => left
2 Do => would
3 visit => visiting
4 play => playing
3 careless
4 bleed
V
1 Hung has colllected stamps since 2000
2 The front yard isn't large enough to play soccer in
3 Milk is delivered twice a week by the milkman
4 When did you bought this computer?
5 His car doesn't run as fasst as a race car
6 Two languages can be spoken well by Lan
VI
1 T
2 F
3 T
4 T
VII
1 Mr. Nam is arriving in Hue tonight
2 They are going back to Englang in two months
3 It is not difficult to tránlate this sentence into English
4 Would you mind lending me your dictionary?
Bài này giải ở dưới r đó
3 careless
4 bleed
V
1 Hung has colllected stamps since 2000
2 The front yard isn't large enough to play soccer in
3 Milk is delivered twice a week by the milkman
4 When did you bought this computer?
5 His car doesn't run as fasst as a race car
6 Two languages can be spoken well by Lan
VI
1 T
2 F
3 T
4 T
VII
1 Mr. Nam is arriving in Hue tonight
2 They are going back to Englang in two months
3 It is not difficult to tránlate this sentence into English
4 Would you mind lending me your dictionary?
3 careless
4 bleed
V
1 Hung has colllected stamps since 2000
2 The front yard isn't large enough to play soccer in
3 Milk is delivered twice a week by the milkman
4 When did you bought this computer?
5 His car doesn't run as fasst as a race car
6 Two languages can be spoken well by Lan
VI
1 T
2 F
3 T
4 T
VII
1 Mr. Nam is arriving in Hue tonight
2 They are going back to Englang in two months
3 It is not difficult to tránlate this sentence into English
4 Would you mind lending me your dictionary?
Tổng 3 số bằng:
4000 x 3= 12000
2/3 số thứ nhất = 1/2 số thứ hai = 2/5 số thứ 3
=> Số thứ hai= 4/3 số thứ nhất
Số thứ hai = 4/5 số thứ 3
=> Xem: Số thứ nhất: 3 phần, số thứ hai 4 phần, số thứ ba 5 phần
Tổng số phần bằng nhau:
3+4+5=12(phần)
Số thứ nhất là:
12000:12 x 3 = 3000
Số thứ hai là:
12000:12 x 4 = 4000
Số thứ ba là:
12000:12 x 5 = 5000
Đáp số: số thứ nhất 3000, số thứ hai 4000, số thứ ba 5000
1 have already made - have just swept - haven't started - did
2 was fighting - started - destroyed
3 will telephone - leaves
4 did you begin - have recently completed - asked
5 has worked - started
6 wanted - chose