Ôn tập chương III

=>6x=5312

=>x=2656/3

Số túi nhiều nhất có thể chia là ước chung lớn nhất của 12; 18 và 30

12 = 2².3

18 = 2.3²

30 = 2.3.5

ƯCLN(12; 18; 30) = 2.3 = 6

Vậy có thể chia nhiều nhất là 6 nhóm

3A=1*2*3+2*3*(4-1)+3*4*(5-2)+...+20*21(23-20)

=21*22*23

=>A=7*22*23=3542

\(1.\dfrac{1\times2+2\times3+3\times4+...+20\times21}{1+2-3-4+5+6-7-8+...197+198-199-200+201}\)

\(=\dfrac{1\cdot21}{1+\left(-5\right)+5+\left(-9\right)+9+...+\left(-197\right)+197+\left(-201\right)+201}\)

\(=\dfrac{21}{1+0+0+0+...+0+0}\)

\(=21\)

a: \(3x^2-4x-4=0\)

\(\Leftrightarrow3x^2-6x+2x-4=0\)

=>(x-2)(3x+2)=0

=>x=2 hoặc x=-2/3

b: \(\Leftrightarrow6x^2+4x-3x-2=0\)

=>(3x+2)(2x-1)=0

=>x=1/2 hoặc x=-2/3

a) \(3x^2+11x+6=10\)

\(\Leftrightarrow3x^2+11x-4=0\)

\(\Leftrightarrow\left(3x-1\right)\left(x+4\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}3x-1=0\\x+4=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{3}\\x=-4\end{matrix}\right.\)

Vậy \(x\in\left\{\dfrac{1}{3};-4\right\}\)

b) \(5x^2-13x+6=0\)

\(\Leftrightarrow\left(5x-3\right)\left(x-2\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}5x-3=0\\x-2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{3}{5}\\x=2\end{matrix}\right.\)

Vậy \(x\in\left\{\dfrac{3}{5};2\right\}\)

`a)`\(3x^2+11x+6=10\)

\(\Rightarrow3x^2+11x-4=0\)

\(\Rightarrow3x^2-x+12x-4=0\)

\(\Rightarrow3x\left(3x-1\right)+4\left(3x-1\right)=0\)

\(\Rightarrow\left(x+4\right)\left(3x-1\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}x=-4\\x=\dfrac{1}{3}\end{matrix}\right.\)

`b)`\(5x^2-13x+6=0\)

\(\Rightarrow5x^2-10x-3x+6=0\)

\(\Rightarrow5x\left(x-2\right)-3\left(x-2\right)=0\)

\(\Rightarrow\left(x-2\right)\left(5x-3\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}x=2\\x=\dfrac{3}{5}\end{matrix}\right.\)

d)

<=>

\(\left(\dfrac{2x}{2}+\dfrac{11}{2}\right)=\dfrac{1}{2}+3+\dfrac{7}{3}=\dfrac{35}{6}\)

<=>

\(\dfrac{2x+11}{2}=\dfrac{35}{6}\)

<=>

\(\dfrac{3\left(2x+11\right)}{6}=\dfrac{35}{6}\)

=> \(6x+33-35=0\)

=> 6x = 0 + 35 - 33 = 2 

=> x = 2/6 = 1/3

`a)(3/4x-10,5):3=15/8:80%`

`(3/4x-21/2):3=15/8:4/5=75/32`

`3/4x-21/2=75/32xx3=225/32`

`3/4x=225/32+21/2=561/32`

`x=561/32:3/4=187/8`

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`b)[-2]/3+1/3x=3/5:3/2`

`[-2]/3+1/3x=2/5`

`1/3x=2/5+2/3=16/15`

`x=16/15:1/3=16/5`

_______________________________________________________________

`c)(2/9-x):5/6=[-4]/3`

`2/9-x=[-4]/3xx5/6=[-10]/9`

`x=2/9-[-10]/9=4/3`

_______________________________________________________________

`d)(x+11/2)-7/3-3=1/2`

`x+11/2=1/2+7/3+3`

`x+11/2=35/6`

`x=35/6-11/2`

`x=1/3`

`(3/4 x - 10,5) : 3 = 15/8 : 80%`

` (3/4 x - 10,5) : 3 = 15/8 xx 5/4`

`(3/4 x - 10,5) : 3 = 75/32`

`3/4x - 10,5 = 75/32 xx 3`

`3/4x - 10,5 = 225/2`

`3/4x = 225/32 + 10,5`

`3/4x= 561/32`

`x = 561/32 : 3/4`

`x=561/32 xx 4/3`

`x = 187/8`

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` (-2)/3 + 1/3x = 3/5 : 3/2`

` (-2)/3 + 1/3x = 3/5 xx 2/3`

`(-2)/3 + 1/3x = 2/5`

`1/3x = 2/5 - (-2)/3`

`1/3x = 2/5 + 2/3`

`1/3x= 16/15`

`x = 16/15 : 1/3`

`x = 16/15 xx 3`

`x= 16/5`

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`(2/9-x) : 5/6 = (-4)/3`

`2/9 - x = (-4)/3 xx 5/6`

`2/9 - x= (-10)/9`

`x = 2/9 - (-10)/9`

`x = 2/9 + 10/9`

`x = 12/9`

`x=4/3`

_________________________________

` (x + 11/2) - 7/3 - 3 = 1/2`

`x + 11/2 = 1/2 + 7/3 + 3`

`x + 11/2 = 35/6`

`x = 35/6 - 11/2`

`x = 1/3`

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`#BaoL i n h`

`0,9 : (2/5 - x) = 7/5`

`2/5 - x = 0,9 : 7/5`

`2/5 - x = 9/10 : 7/5`

`2/5 - x = 9/10 xx 5/7`

`2/5 - x = 9/14`

`x = 2/5 - 9/14`

`x = -17/70`

`#BaoL i n h`

`0,9 : (2/5 - x) = 7/5`

`2/5 - x = 0,9 : 7/5`

`2/5 - x = 9/10 xx 5/7`

`2/5 - x = 9/14`

`x = 2/5 - 9/14`

`x = -17/70`

0,9 : ( 2/5 - x ) = 7/5 

2/5 - x = 0,9 : 7/5 

2/5 - x = 9/10 : 5/7 

2/5 - x = 9/10 x 5/7 

2/5 - x = 9/14

 x = 2/5 - 9/14 

 x = -17/70 

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