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10 tháng 12 2021

15 + x = 15

       x  = 15 -15

       x  = 0

10 tháng 12 2021

15+x=7-(-8)

15+x=7+8

15+x=15

x=15-15

x=0

vậy x=0

15 tháng 3 2022

\(a\dfrac{3\times8\times7}{7\times11\times3}=\dfrac{8}{11}\)

\(b\dfrac{4}{15}\times\left(\dfrac{3}{8}+\dfrac{5}{8}\right)=\dfrac{4}{15}\times1=\dfrac{4}{15}\)

15 tháng 3 2022

a)8/11

b) (3/8+5/8) x 4/15= 1 x 4/15= 4/15

1) Ta có: \(\left(\dfrac{3}{4}\cdot\dfrac{5}{97}+\dfrac{1}{9}\cdot\dfrac{13}{47}\right)\cdot\left(\dfrac{1}{5}-\dfrac{7}{25}\cdot\dfrac{5}{7}\right)\)

\(=\left(\dfrac{3}{4}\cdot\dfrac{5}{97}+\dfrac{1}{9}\cdot\dfrac{13}{47}\right)\cdot\left(\dfrac{1}{5}-\dfrac{1}{5}\right)\)

=0

2) Ta có: \(\dfrac{8}{17}\cdot\dfrac{4}{15}+\dfrac{8}{17}\cdot\dfrac{22}{15}-\dfrac{8}{15}\cdot\dfrac{9}{17}\)

\(=\dfrac{8}{17}\left(\dfrac{4}{15}+\dfrac{22}{15}-\dfrac{9}{15}\right)\)

\(=\dfrac{8}{17}\cdot\dfrac{15}{15}=\dfrac{8}{17}\)

3) Ta có: \(\dfrac{2021}{2}\cdot\dfrac{1}{3}+\dfrac{4042}{4}\cdot\dfrac{1}{5}+\dfrac{6063}{3}\cdot\dfrac{22}{15}\)

\(=\dfrac{2021}{2}\left(\dfrac{1}{3}+\dfrac{1}{5}\right)+2021\cdot\dfrac{22}{15}\)

\(=\dfrac{2021}{2}\cdot\dfrac{8}{15}+\dfrac{2021}{2}\cdot\dfrac{44}{15}\)

\(=\dfrac{2021}{2}\cdot\dfrac{52}{15}\)

\(=\dfrac{52546}{15}\)

4) Ta có: \(\dfrac{4}{7}\cdot\dfrac{2}{13}+\dfrac{8}{13}:\dfrac{7}{4}+\dfrac{4}{7}:\dfrac{13}{2}+\dfrac{4}{7}\cdot\dfrac{1}{13}\)

\(=\dfrac{4}{7}\left(\dfrac{2}{13}+\dfrac{8}{13}+\dfrac{2}{13}+\dfrac{1}{13}\right)\)

\(=\dfrac{4}{7}\)

2 tháng 7 2021

cảm ơn nhé

vui

2 tháng 2 2016

7/13 x 7/15 - 5/12 x 7/13 + 7/13 x 8/15 =7/13x(7/15-5/12+8/15)=7/13x7/12=49/156

1 tháng 3

12/13×8/15×7/9=........................

                                ........................

9 tháng 10 2018

`@` `\text {Ans}`

`\downarrow`

`x^3 = 125`

`=> x^3 = 5^3`

`=> x = 5`

Vậy, `x = 5`

_____

`4^5 \div 4^3`

`=`\(4^{5-3}\)

`= 4^2`

______

\(8^{12}\cdot8^3\div8^{15}\)

`=`\(8^{12+3-15}\)

`=`\(8^0=1\)

______

\(7^{15}\div7^{13}\)

`=`\(7^{15-13}\)

`=`\(7^2\)

_______

\(17^{15}\cdot17^{10}\div17^{22}\)

`=`\(17^{15+10-22}\)

`= 17^3`

_______

\(5^{10}\cdot25\div5^{11}\)

`=`\(5^{10}\cdot5^2\div5^{11}\)

`=`\(5^{10+2-11}\)

`= 5`

_______

\(15^{10}\cdot225\div15^{11}\)

`=`\(15^{10}\cdot15^2\div15^{11}\)

`=`\(15^{12}\div15^{11}\)

`= 15`

`@` `\text {Kaizuu lv uuu}`

10 tháng 7 2023

\(x^3=125\)

\(\Rightarrow x^3=5^3\)

\(\Rightarrow x=3\)

___________________

\(4^5:4^3\)

\(=4^{5-3}\)

\(=4^2=16\)

 

___________________

\(8^{12}.8^3:8^{15}\)

\(=8^{15}:8^{15}\)

\(=1\)

___________________

\(7^{15}:7^{13}\)

\(=7^{15-13}\)

\(=7^2=49\)

___________________

\(17^{15}.17^{10}:17^{22}\)

\(=17^{25}:17^{22}\)

\(=17^3=4913\)

___________________

\(5^{10}.25:5^{11}\)

\(=5^{10}.5^2:5^{11}\)

\(=5^{12}:5^{11}\)

\(=5^1=5\)

___________________

\(15^{10}.225:15^{11}\)

\(=15^{10}.15^2:15^{11}\)

\(=15^{12}:15^{11}\)

\(=15^1=15\)

__________________

* a. a= an+m

 an : am = an-m

Chúc bạn học tốt

7 tháng 4 2022

\(\dfrac{2}{1}+\dfrac{12}{56}=\dfrac{112+12}{56}=\dfrac{122}{56}=\dfrac{61}{28}\)

\(\left(\dfrac{8+7}{15}\right):\dfrac{2}{11}\)

\(1:\)\(\dfrac{2}{11}\)

\(\dfrac{11}{2}\)

8 tháng 4 2022

\(\dfrac{2}{1}+\dfrac{12}{56}=\dfrac{112}{56}+\dfrac{12}{56}=\dfrac{122}{56}=\dfrac{61}{28}\)

   

 

\(=\left(\dfrac{8}{15}+\dfrac{7}{15}\right)\times\dfrac{11}{2}=\dfrac{15}{15}\times\dfrac{11}{2}=1\times\dfrac{11}{2}=\dfrac{11}{2}\)

Câu 30:

\(\dfrac{x+1}{8}=\dfrac{2}{x+1}\)

=>\(\left(x+1\right)^2=2\cdot8=16\)

=>\(\left[{}\begin{matrix}x+1=4\\x+1=-4\end{matrix}\right.\)

=>\(\left[{}\begin{matrix}x=3\\x=-5\end{matrix}\right.\)

=>Chọn D

Câu 31:

\(-\dfrac{7}{15}\cdot\dfrac{5}{8}\cdot\dfrac{15}{-7}\cdot\left(-16\right)\)

\(=\dfrac{5}{8}\cdot\left(-16\right)=-10\)

=>Chọn D

17 tháng 3 2022

câu 31 : D 

17 tháng 3 2022

giúp mik câu 30 luôn dc ko bạn