\(\dfrac{2}{5}\times\dfrac{7}{6}-\dfrac{3}{15}\)

\(=\dfrac{2\times7}{5\times6}-\dfrac{3}{15}\)

\(=\dfrac{7}{5\times3}-\dfrac{3}{15}\)

\(=\dfrac{7}{15}-\dfrac{3}{15}\)

\(=\dfrac{4}{15}\)

\(S=\left(1-2\right)+\left(3-4\right)+\left(5-6\right)+...+\left(199-200\right)+201\)

\(S=\left(-1\right)+\left(-1\right)+\left(-1\right)+...+\left(-1\right)+201\)

Số số hạng là :

\(\left(200-1\right):1+1=200\) (số hạng)

Tổng dãy là :

\(200:2=100\) (cặp)

\(S=-100+201\)

\(S=101\)

\(\left(4x^2\right)^8\cdot\left(4x^2\right)\cdot\left(4x^2\right)^2\)

\(=\left[\left(2x\right)^2\right]^8\cdot\left[\left(2x\right)^2\right]^4\cdot\left[\left(2x\right)^2\right]^2\)

\(=\left(2x\right)^{16}\cdot\left(2x\right)^8\cdot2x^4\)

\(=\left(2x\right)^{28}\)

`4x^3 +20=52`

`=> 4x^3=52-20`

`=> 4x^3= 32`

`=>x^3=32:4`

`=x^3=8`

`=>x^3=2^3`

`=>x=2`

Vậy `x=2`

Cậu viết lại đề được không ạ?

\(\dfrac{2^7\cdot9^3}{6^5\cdot8^2}\\ =\dfrac{2^7\cdot\left(3^2\right)^3}{\left(2\cdot3\right)^5\cdot\left(2^3\right)^2}\\ =\dfrac{2^7\cdot3^6}{2^5\cdot3^5\cdot2^6}\\ =\dfrac{2^2\cdot3}{2^6}\\ =\dfrac{4\cdot3}{64}\\ =\dfrac{12}{64}\\ =\dfrac{3}{16}\)