tr may quá;-; chúc mừng các bạn nha='))

\(\left(25\cdot21+25\cdot51\right):36\\ =\left[25\cdot\left(21+51\right)\right]:36\\ =\left(25\cdot72\right):36\\ =1800:36\\ =50\\ \left\{188-\left[33+\left(6^2-7\cdot3\right)\right]\right\}:70\\ =\left\{188-\left[33+\left(36-21\right)\right]\right\}:70\\ =\left[188-\left(33+15\right)\right]:70\\ =\left(188-48\right):70\\ =140:70\\ =2\)

\(\left(x-1\right)\left(15-3x\right)=0\\ \Rightarrow\left[{}\begin{matrix}x-1=0\\15-3x=0\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}x=1\\3x=15\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=1\\x=5\end{matrix}\right.\)

\(720:\left[41-\left(2x+5\right)\right]=2^3\cdot5=8\cdot5\\ \Rightarrow720:\left[41-\left(2x+5\right)\right]=40\\ \Rightarrow41-\left(2x+5\right)=720:40\\ \Rightarrow41-\left(2x+5\right)=18\\ \Rightarrow2x+5=41-18\\ \Rightarrow2x+5=23\\ \Rightarrow2x=23-5\\ \Rightarrow2x=18\\ \Rightarrow x=18:2\\ \Rightarrow x=9\)

không để ý dấu giá trị tuyệt đối, cảm ơn c nhé!

`2^3 * 19 - 2^3 -14 +1^(2021)`

`= 8 *19 - 8-14 +1`

`= 152 -8-14+1`

`=144-14+1`

`=130+1`

`=131`

\(64\cdot4^x=16^8\\ \Rightarrow4^3\cdot4^x=\left(4^2\right)^8\\ \Rightarrow4^3\cdot4^x=4^{16}\\ \Rightarrow4^x=4^{16}:4^3\\ \Rightarrow4^x=4^{13}\\ \Rightarrow x=13\)

Vậy `x=13`

`3x+45=195`

`=>3x=195-45`

`=> 3x= 150`

`=>x=150:3`

`=>x= 50`

vậy `x=50`

`5^6 : 5^3 +3^2 : 3^3 - 3^4 . 3`

`= 5^(6-3)+  (3^2)/(3^3) - 3^(4+1)`

`= 5^3 + 9/27 - 3^5`

`= 125 + 1/3 -243`

`=-353/3`

\(\left(x-2y\right)\left(x^2+2xy+4y^2\right)-\left(x-y\right)\left(x^2+8y^2\right)\\ =x^3-8y^3-\left(x^3+8y^3-x^2y-8y^3\right)\\ =x^3-8y^3-x^3-8y^3+x^2y+8y^3\\ =-8y^3+x^2y\)