`@` `\text {Ans}`

`\downarrow`

Ta có:

\(5x=4y\Rightarrow\dfrac{x}{4}=\dfrac{y}{5}\)

Áp dụng tính chất dãy tỉ số bằng nhau ta có:

\(\dfrac{x}{4}=\dfrac{y}{5}=\dfrac{x-y}{4-5}=\dfrac{7}{-1}=-7\)

\(\Rightarrow\dfrac{x}{4}=\dfrac{y}{5}=-7\)

\(\Rightarrow x=-7\cdot4=-28\)

\(y=-7\cdot5=-35\)

Vậy, `x = -28; y = -35`

Giup mik với

`@` `\text {Ans}`

`\downarrow`

Áp dụng tính chất dãy tỉ số bằng nhau ta có:

\(\dfrac{x}{5}=\dfrac{y}{4}=\dfrac{z}{7}=\dfrac{x+y+z}{5+4+7}=\dfrac{40}{16}=\dfrac{5}{2}=2,5\)

`=>`\(\dfrac{x}{5}=\dfrac{y}{4}=\dfrac{z}{7}=2,5\)

`=> x = 2,5. 5 = 12,5`

`y = 2,5.4 = 10`

`z = 2,5.7 = 17,5`

Vậy, `x = 12,5`; `y = 10;` `z = 17,5.`

Nhanh giúp mik với

\(\left(-\dfrac{3}{4}+\dfrac{2}{5}\right):\dfrac{3}{7}+\left[\dfrac{3}{5}+\left(-\dfrac{1}{4}\right)\right]:\dfrac{3}{7}\)

\(=\left(-\dfrac{3}{4}+\dfrac{2}{5}\right):\dfrac{3}{7}+\left(\dfrac{3}{5}-\dfrac{1}{4}\right):\dfrac{3}{7}\)

\(=-\dfrac{7}{20}:\dfrac{3}{7}+\dfrac{7}{20}:\dfrac{3}{7}\)

\(=-\dfrac{7}{20}.\dfrac{7}{3}+\dfrac{7}{20}.\dfrac{7}{3}=\left(-\dfrac{7}{20}+\dfrac{7}{20}\right).\dfrac{7}{3}\)

\(=0.\dfrac{7}{3}=0\)

thiếu dữ liệu bạn nhé!

\(\dfrac{1}{3}-\dfrac{1}{3}x=\dfrac{1}{5}\cdot\dfrac{30}{7}\)

\(\Rightarrow\dfrac{1}{3}-\dfrac{1}{3}x=\dfrac{6}{7}\)

\(\Rightarrow\dfrac{1}{3}x=\dfrac{1}{3}-\dfrac{6}{7}\)

\(\Rightarrow\dfrac{1}{3}x=-\dfrac{11}{21}\)

\(\Rightarrow x=-\dfrac{11}{21}:\dfrac{1}{3}\)

\(x=-\dfrac{11}{7}\)

Vậy \(x=-\dfrac{11}{7}\)

      A =         \(\dfrac{1}{2}\) - \(\dfrac{1}{2^2}\) + \(\dfrac{1}{2^3}\) - \(\dfrac{1}{2^4}\)+...+ \(\dfrac{1}{2^{99}}\) - \(\dfrac{1}{2^{100}}\)

     2A =   1 - \(\dfrac{1}{2}\) + \(\dfrac{1}{2^2}\) - \(\dfrac{1}{2^3}\) + \(\dfrac{1}{2^3}\)-...-\(\dfrac{1}{2^{99}}\) 

2A + A =   1 - \(\dfrac{1}{2^{100}}\)

3A       = ( 1 - \(\dfrac{1}{2^{100}}\))

   A       = (1 -  \(\dfrac{1}{2^{100}}\)): 3

   A        = \(\dfrac{1}{3}\) - \(\dfrac{1}{3.2^{100}}\)

\(\)L1\(\dfrac{ }{ }\) bạn chi cần nhân biểu tgucws với rồi lấy 2 lần biểu thức ấy - đi biểu thức bán đầu

\(\dfrac{4^{18}.9^{15}}{6^{18}}=\dfrac{2^{46}.3^{30}}{2^{18}.3^{18}}=2^{46-18}.3^{30-18}=2^{28}.3^{12}\)

4¹⁸ x 9¹⁵ /6¹⁸

=(2²)18 x (3²)¹⁵ /2¹⁸ x 3¹⁸

=2³⁶ x 3³⁰ /2¹⁸ x 3¹⁸

=2^36-18 x 3^30-18 

=2¹⁸ x 3¹²

=(2³)⁶ x (3²)⁶

=8⁶ x 9⁶ =72⁶