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a. ( x + 1 ) ( x + 2 ) ( x - 3 )
= ( x2 + 3x + 2 ) ( x - 3 )
= x3 + 3x2 + 2x - 3x2 - 9x - 6
= x3 - 7x - 6
b. ( 2x - 1 ) ( x + 2 ) ( x + 3 )
= ( 2x2 + 3x - 2 ) ( x + 3 )
= 2x3 + 3x2 - 2x + 6x2 + 9x - 6
= 2x3 + 9x2 + 7x - 6
a) ( x + 1 )( x + 2 )( x - 3 )
= ( x2 + 3x + 2 )( x - 3 )
= x3 - 3x2 + 3x2 - 9x + 2x - 6
= x3 - 7x - 6
b) ( 2x - 1 )( x + 2 )( x + 3 )
= ( 2x2 + 3x - 2 )( x + 3 )
= 2x3 + 6x2 + 3x2 + 9x - 2x - 6
= 2x3 + 9x2 + 7x - 6
\(BPT\Leftrightarrow\left(2+\sqrt{x^2-2x+5}\right)\left(x+1\right)+\frac{2x\left(3x^2+2x-1\right)}{2\sqrt{x^2+1}+\sqrt{x^2-2x+5}}\le0\)
\(\Leftrightarrow\left(2+\sqrt{x^2-2x+5}\right)\left(x+1\right)+\frac{2x\left(x+1\right)\left(3x-1\right)}{2\sqrt{x^2+1}+\sqrt{x^2-2x+5}}\le0\)
\(\Leftrightarrow\left(x+1\right)\text{[}2+\sqrt{x^2-2x+5}+\frac{2x\left(3x-1\right)}{2\sqrt{x^2+1}+\sqrt{x^2-2x+5}}\text{]}\le0\)
\(\Leftrightarrow\left(x+1\right)\left(4\sqrt{x^2+1}+2\sqrt{x^2-2x+5}+2\sqrt{\left(x^2+1\right)\left(x^2-2x+5\right)}+7x^2-4x+5\right)\)\(\le0\Leftrightarrow x+1\le0\Leftrightarrow x\le-1\)
đk: \(x\ne0\)
Ta có:
\(D=x+\sqrt{x^2+\frac{1}{x^2}+2}\)
\(D=x+\sqrt{\left(x+\frac{1}{x}\right)^2}\)
\(D=x+\left|x+\frac{1}{x}\right|\)
\(D=x-x-\frac{1}{x}\) \(\left(x< 0\right)\)
\(D=-\frac{1}{x}\)
Sửa 135 thành 137 chứ nếu để như vậy làm sao mà tính <...
Bài giải
\(\left(1+2+3+...+2020\right)\left(135\cdot137\cdot137-137\cdot137\cdot135\right)\)
\(=\left(1+2+3+...+2020\right)\cdot0=0\)
\(\left(1+2+3+...+2020\right).\left(135.135.137-137.137.135\right)\)
\(=2021.1010.\left(135.135.137-137.\left(135+2\right).135\right)\)
\(=204121.\left(135^2.137-137^2.135\right)\)
\(=204121.\left(\left(135-137\right)^2.\left(137-135\right)\right)\)
\(=204121.\left(-2^2.2\right)\)
\(=204121.-8\)
\(=-1632968\)
Đúng chưa?
I ) Comphete the sentence with the correct form of the verb
.Children often ...use.........( use ) a comphute for school work
( Thì HTĐ )
Có:x+y =1 => (x+y)2 = 1 => x2 + y2 = 1-2xy
\(\frac{x}{y+1}+\frac{y}{x+1}=\frac{x\left(x+1\right)+y\left(y+1\right)}{\left(y+1\right)\left(x+1\right)}=\frac{x^2+x+y^2+y}{yx+y+x+1}=\frac{1-2xy+1}{yx+2}\)\(=\frac{2-2xy}{2+yx}\)
Vì x,y không âm
=> \(-xy\le xy\)
=> \(-2xy\le xy\)
=>\(2-2xy\le2+xy\)
=> \(\frac{2-2xy}{2+xy}\le1\)
=> đpcm
Bài 1: Tìm x biết
a) x - 50 : 25 = 8
x- 2 = 8
x= 8+2
x=10
b) (x + 40).15 = 75.24
x+40 = 75.24:15
x+40 = 70
x= 30
c) (x - 32) - 15 = 0
x- 31 = 15
x= 15+ 31
x = 46
d) 1234 : x = 2
x= 1234:2
x = 617
e) (x - 34).26 = 0
x- 34 = 0: 26
x= 0 + 34
x= 34
f) 152 + (x + 231) : 2 = 358
(x+231):2 = 358- 152
(x+231):2 = 206
x+ 231 = 206*2
x= 412 - 231
x= 181
1.
a) x - 50 : 25 = 8
x - 2 = 8
x = 10
b) (x + 40) . 15 = 75 . 24
x + 40 = 75 . 24 : 15
x + 40 = 120
x = 80
c) (x - 32) - 15 = 0
x - 32 = 15
x = 47
d) 1234 : x = 2
x = 617
e) (x - 34) . 26 = 0
Thỏa mãn điều kiện x - 34 = 0
x = 34
f) 152 + (x + 231) : 2 = 358
(x + 231) : 2 = 206
x + 231 = 412
x = 181
2.
a) 45 . (2 . x - 4) . 13 = 0
Thỏa mãn điều kiện 2 . x - 4 = 0
x = 2
b) 5 . x - 38 : 19 = 13
5 . x - 2 = 13
5 . x = 15
x = 3
c) 100 - 3 . (8 + x) = 1
3 . (8 + x) = 99
8 + x = 33
x = 25
d) [(x + 12) - 17] : 5 = 4
(x + 12) - 17 = 20
x + 12 = 37
x = 25
e) 84 - 4 . (2 . x + 1) = 48
4 . (2 . x + 1) = 36
2 . x + 1 = 9
2 . x = 8
x = 4
1. B, sửa: to visit
2. A, sửa: is always
3. A, sửa:How much
Học tốt nhá :))
Find mistake in the four underline part A,B,C,D of each sentences
1. Hoa is going visit her grandparents tommorow morning => to visit ( TLG)
A B C D
2.Thuy always is late for school in the morning => bỏ : '' is''
A B C D
3. How many milk does Mr. Hai's cow produce ? A little => How much ( milk không đếm đc )
A B C D
