mọi người giúp mình với ạ,mình cảm ơn rất nhiều
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12 tháng 3 2022
Bài 1 :
Thay x = 2 ; y = -1/2 ta được
\(B=-8+2.4\left(-\dfrac{1}{2}\right)-4.2.\left(\dfrac{1}{4}\right)+2\left(-\dfrac{1}{2}\right)-3\)
\(=-8-4-2-1-3=-18\)
6 tháng 2 2021
a) Ta có: \(\left(2x-3\right)\left(3x+4\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}2x-3=0\\3x+4=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}2x=3\\3x=-4\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{3}{2}\\x=-\dfrac{4}{3}\end{matrix}\right.\)
Vậy: \(S=\left\{\dfrac{3}{2};-\dfrac{4}{3}\right\}\)
b) Ta có: \(x^3-3x^2+3x-1=\left(x-1\right)\left(x+1\right)\)
\(\Leftrightarrow\left(x-1\right)^3-\left(x-1\right)\left(x+1\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left[x^2-2x+1-x-1\right]=0\)
\(\Leftrightarrow\left(x-1\right)\left(x^2-3x\right)=0\)
\(\Leftrightarrow x\left(x-1\right)\left(x-3\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x-1=0\\x-3=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=1\\x=3\end{matrix}\right.\)
Vậy: S={0;1;3}
c) Ta có: \(x^2+x=2x+2\)
\(\Leftrightarrow x\left(x+1\right)-2\left(x+1\right)=0\)
\(\Leftrightarrow\left(x+1\right)\left(x-2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x+1=0\\x-2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-1\\x=2\end{matrix}\right.\)
Vậy: S={-1;2}
d) Ta có: \(\left(x-1\right)^2=2\left(x^2-1\right)\)
\(\Leftrightarrow\left(x-1\right)^2-2\left(x-1\right)\left(x+1\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left(x-1-2x-2\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left(-x-3\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-1=0\\-x-3=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1\\-x=3\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-3\end{matrix}\right.\)Vậy: S={1;-3}
e) Ta có: \(2\left(x+2\right)^2-x^3-8=0\)
\(\Leftrightarrow2\left(x+2\right)^2-\left(x^3+8\right)=0\)
\(\Leftrightarrow2\left(x+2\right)\cdot\left(x+2\right)-\left(x+2\right)\left(x^2-2x+4\right)=0\)
\(\Leftrightarrow\left(x+2\right)\left(2x+4-x^2+2x-4\right)=0\)
\(\Leftrightarrow\left(x+2\right)\cdot\left(-x^2+4x\right)=0\)
\(\Leftrightarrow-x\left(x+2\right)\left(x-4\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x+2=0\\x-4=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-2\\x=4\end{matrix}\right.\)
Vậy: S={0;-2;4}
31 tháng 10 2021
a: \(P=-\left|5-x\right|+2019\le2019\forall x\)
Dấu '=' xảy ra khi x=5
TN
Mọi người ơi giúp mình với,mình cảm ơn rất nhiều ạ
2
S
22 tháng 1 2022
used to deliver
used to be
used to go
used to drive
used to spend
used to believe
used to work
used to serve
LP
22 tháng 1 2022
1. used to deliver
2. used to be
3. used to go
4. used to drive
5. used to spend
6. used to believe
7.used to work
8. used to serve
19 tháng 6 2023
1. Mohenjo-Daro was one of the first city.
2. If we look at a map of Mohenjo-Daro, we can see the straight street.
3. Rome was the capital of the Roman Republic and Empire for a thousand years.
4. London was the biggest city in the world between 1831 and 1925.
5. Tokyo is the biggest city in the world now.
DT
Đỗ Thanh Hải
CTVVIP
25 tháng 3 2021
IV
1 to have
2 making
3 leaving
4 seeing
5 to get
6 arguing - working
7 to have
8 to seeing
9 not touching
10 to disappoint
V
1 on - on
2 at - at
3 in - in
4 at
5 at
6 in
7 in - in
8 at - in
9 in - at
10 in
VI
1 are - reach
2 comes
3 flies
4 have just decided - will undertake
5 would take
6 was
8 am attending - was attending
9 arrived - was waiting
10 had lived
VII
1 send - will receive
2 will - improve - do
3 will - has
4 doesn't phone - will leave
DT
Đỗ Thanh Hải
CTVVIP
25 tháng 3 2021
tờ 2
5 don't study - won't oas
VIII
1 had - would learn
2 told - would be
3 lived - would do
4 would help - knew
5 would buy - had
IX
1 went
2 were
3 wrote
4 could
5 bought
6 studied
7 went
8 would stop
9 were
10 lead
X
1 He opened the window in order to let fresh air in
2 I took my camera so that I could take some phôt
3 He studied really hard in order to get better marks
4 Jason learns Chinese to work in China
5 I've collected money in order that I will buy a new car
XI
1 A new museum has been built in the city center by the council
2The explosion had been caused by a bomb
3 Their flat was broken into last month
4 Jane won't be invited to his birthday party by him
