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9 tháng 9 2018

Giải sách bài tập Toán 8 | Giải bài tập Sách bài tập Toán 8

20 tháng 12 2021

Chọn B

Đề có sai không bạn?

10 tháng 7 2023

`1, -2/9 xx 15/17 + (-2/9) xx 2/17`

`= -2/9 xx (15/17 + 2/17)`

`= -2/9 xx 17/17`

`=-2/9xx1`

`=-2/9`

__

`-5/3 xx 6/5 + (-7/9) xx 3/10`

`= -30/15 + (-21/90)`

`= -2 + (-7/30)`

`=-60/30 +(-7/30)`

`=-67/30`

__

`15/20 xx 7/5 + (-9/7) xx (-6/4)`

`=3/4 xx7/5 + (-9/7) xx(-6/4)`

`= 21/20 + 54/28`

`= 21/20 + 27/14`

`=417/140`

__

`-25/13 xx 5/19 + (-25/13) xx 14/19`

`=-25/13 xx (5/19 +14/19)`

`=-25/13 xx 19/19`

`= -25/13 xx 1`

`=-25/13`

__

`-7/13 xx 13/5 + (-9/7) xx 5/3`

`=-7/5 +(-15/7)`

`=-124/35`

1: =-2/9(15/17+2/17)=-2/9

2: \(=\dfrac{-6}{3}+\dfrac{-21}{90}\)

=-2-7/30=-67/30

3: \(=\dfrac{3}{4}\cdot\dfrac{7}{5}+\dfrac{9}{7}\cdot\dfrac{3}{2}\)

=21/20+27/14=417/140

4: =-25/13(5/19+14/19)=-25/13

5: =-7/5-45/21=-7/5-15/7=-124/35

10 tháng 7 2023

1: =-2/9(15/17+2/17)=-2/9

2: =−63+−2190=−63+−2190

=-2-7/30=-67/30

3: =34⋅75+97⋅32=34⋅75+97⋅32

=21/20+27/14=417/140

4: =-25/13(5/19+14/19)=-25/13

5: =-7/5-45/21=-7/5-15/7=-124/35

23 tháng 4 2022

bn đăng bên toán nhé

1) Ta có: \(\left(-\dfrac{2}{3}\right)^2\cdot\dfrac{-9}{8}-25\%\cdot\dfrac{-16}{5}\)

\(=\dfrac{4}{9}\cdot\dfrac{-9}{8}-\dfrac{1}{4}\cdot\dfrac{-16}{5}\)

\(=\dfrac{-1}{2}+\dfrac{4}{5}\)

\(=\dfrac{-5}{10}+\dfrac{8}{10}=\dfrac{3}{10}\)

2) Ta có: \(-1\dfrac{2}{5}\cdot75\%+\dfrac{-7}{5}\cdot25\%\)

\(=\dfrac{-7}{5}\cdot\dfrac{3}{4}+\dfrac{-7}{5}\cdot\dfrac{1}{4}\)

\(=\dfrac{-7}{5}\left(\dfrac{3}{4}+\dfrac{1}{4}\right)=-\dfrac{7}{5}\)

3) Ta có: \(-2\dfrac{3}{7}\cdot\left(-125\%\right)+\dfrac{-17}{7}\cdot25\%\)

\(=\dfrac{-17}{7}\cdot\dfrac{-5}{4}+\dfrac{-17}{7}\cdot\dfrac{1}{4}\)

\(=\dfrac{-17}{7}\cdot\left(\dfrac{-5}{4}+\dfrac{1}{4}\right)\)

\(=\dfrac{17}{7}\)

4) Ta có: \(\left(-2\right)^3\cdot\left(\dfrac{3}{4}\cdot0.25\right):\left(2\dfrac{1}{4}-1\dfrac{1}{6}\right)\)

\(=\left(-8\right)\cdot\left(\dfrac{3}{4}\cdot\dfrac{1}{4}\right):\left(\dfrac{9}{4}-\dfrac{7}{6}\right)\)

\(=\left(-8\right)\cdot\dfrac{3}{16}:\dfrac{54-28}{24}\)

\(=\dfrac{-3}{2}\cdot\dfrac{24}{26}\)

\(=\dfrac{-72}{52}=\dfrac{-18}{13}\)

a: =>(x-2)^3*[(x-2)^8-1]=0

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

=>\(x\in\left\{2;3;1\right\}\)

b: (x-5)^24=(x-5)^9

=>\(\left(x-5\right)^9\cdot\left[\left(x-5\right)^{15}-1\right]=0\)

=>x-5=0 hoặc x-5=1

=>x=6 hoặc x=5

c: =>(x-5)^4*[(x-5)^21-1]=0

=>x-5=0 hoặc x-5=1

=>x=5 hoặc x=6

31 tháng 7 2023

a) \(\left(x-2\right)^{11}=\left(x-2\right)^3\)

\(\Rightarrow\left(x-2\right)^{11}-\left(x-2\right)^3=0\)

\(\Rightarrow\left(x-2\right)^3\left[\left(x-2\right)^8-1\right]=0\)

\(\Rightarrow\left[{}\begin{matrix}\left(x-2\right)^3=0\\\left(x-2\right)^8-1=0\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x-2=0\\\left(x-2\right)^8=1\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=2\\x-2=1\end{matrix}\right.\)

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

b) \(\left(x-5\right)^{24}=\left(x-5\right)^9\)

\(\Rightarrow\left(x-5\right)^{24}-\left(x-5\right)^9=0\)

\(\Rightarrow\left(x-5\right)^9\left[\left(x-5\right)^{15}-1\right]=0\)

\(\Rightarrow\left[{}\begin{matrix}\left(x-5\right)^9=0\\\left(x-5\right)^{15}-1=0\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x-5=0\\\left(x-5\right)^{15}=1\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=5\\x-5=1\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=5\\x=6\end{matrix}\right.\)

c) \(\left(x-5\right)^{25}=\left(x-5\right)^4\)

\(\Rightarrow\left(x-5\right)^{25}-\left(x-5\right)^4\)

\(\Rightarrow\left(x-5\right)^4\left[\left(x-5\right)^{21}-1\right]=0\)

\(\Rightarrow\left[{}\begin{matrix}\left(x-5\right)^4=0\\\left(x-5\right)^{21}-1=0\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x-5=0\\\left(x-5\right)^{21}=1\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=5\\x-5=1\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=5\\x=6\end{matrix}\right.\)

27 tháng 11 2021

1. A

2. B

3. A

4. B

1.    444 x 5 = 222 x 2 x 5 = 222 x 10 = 2220
a.Đúng    b.Sai

2.    282 x 5 = 280 + 2 x 5 = 280 x 10 = 2800
a.Đúng      b. Sai

3.    4 x 8 x 7 x 25 = (8 x 7) x (25 x4) = 56 x 100 = 5600
a.Đúng      b.Sai

4.    25 x 8 x 9 = (25 x 4) x (4 x 9) = 100 x 36 = 3600
a.Đúng         b.Sai