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ĐKXĐ : 2x \(\ge\)0 <=> x \(\ge\)0
| 7 + x | = 2x <=> \(\orbr{\begin{cases}7+x=2x\\7+x=-2x\end{cases}}\)
<=> \(\orbr{\begin{cases}x=7\\x=\frac{-7}{3}\end{cases}}\)( KTMĐK)
Vậy x = 7
9 will have to
10 must work
11 will you do - fail
12 will you do
13 were - would buy
14 were - would help
15 had - would travel
16 had - would go
17 would tell - were
18 knew - would speak
19 gets - will go
20 can play - is
21 isn't raining - will have
22 had - would finish
23 wouldn't do - were
24 didn't speak
25 would buy - had
26 weren't - would buy
27 goes
28 will she go
29 would you do - were
30 were - would help
31 would you buy - were
32 would she do - were
33 will they do - become
34 would Ba go - had
35 had been - would have helped
36 had had - would have bought
37 hadn't bought - would have bought
38 would have been - hadn't rained
39 wouldn't have done
40 would have bought
41 would you do
42 would you have done
43 would you have done
44 would you have bought
45 has
46 would have come
III.
1 I will visit you
2 I would travel around the world
3 we will fail the final term test
4 you should take care of her
5 I would run away
6 we will go on a picnic
7 I would have got a good mark
8 he wouldn't be so fat now
9 I would kill it
4 số có TBC bằng 8 là 4;6;10;12
=>Hai số còn lại là 2;8
Trung bình cộng là (2+8)/2=5
Ta có: \(\left(3x+2\right)^3-3x\left(3x+4\right)^2-17x\left(x-3\right)=-54\)
\(\Leftrightarrow27x^3+54x^2+36x+8-3x\left(9x^2+24x+16\right)-17x^2+51x=-54\)
\(\Leftrightarrow27x^3+37x^2+87x+8+54-27x^3-72x^2-48x=0\)
\(\Leftrightarrow-35x^2+39x+62=0\)
\(\Delta=39^2-4\cdot\left(-35\right)\cdot62=10201\)
Vì \(\Delta>0\) nên phương trình có hai nghiệm phân biệt là:
\(\left\{{}\begin{matrix}x_1=\dfrac{-39-101}{-70}=\dfrac{-140}{-70}=2\\x_2=\dfrac{-39+101}{-70}=\dfrac{-62}{70}=\dfrac{-31}{35}\end{matrix}\right.\)
x(y-1)+2(y-1)=1
(y-1).((x+2)=1
y-1=1 hoặc x+2=1=>y=2 hoặc x=-1
y-1=-1 hoặc x+2=-1=>y=0 hoặc x=-3
Vậy: (x;y)= (-1;2) ; (-3;0)
\(\left|2x-3\right|=3-2x\)
\(ĐK:x\le\dfrac{3}{2}\)
\(\Leftrightarrow\left[{}\begin{matrix}2x-3=3-2x\\3-2x=3-2x\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{3}{2}\\0=0\left(đúng\right)\end{matrix}\right.\)
Vậy \(S=\left\{x\in R;x=\dfrac{3}{2}\right\}\)
suy ra 3x-3-x-5=-18
(3x-x)-(3+5)=-18
2x-8=-18
2x=-18+8
2x=-10
x=-10/2
x=-5
gọi số ngỗng là x
=> số ngan là x+125
số vịt là 2x+125
theo đề bài ta có :
x + x+125 +2x +125 =1350
4x + 250 =1350
4x =1100
x =275
=> số ngỗng là 275(con)
số ngan là 275+ 125=400(con)
số vịt là 275 + 400 =675 (con)
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