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`1)`

`A=1800:{450:[450-(4.5^3-2^3 . 5^2)]}`

`A=1800:{450:[450-(4.125-8.25)]}`

`A=1800:{450:[450-(500-200)]}`

`A=1800:[450:(450-300)]`

`A=1800:(450:150)`

`A=1800:3`

`A=600`

`-` Vậy : `A=600.`

`B={5.4^15. 9^9-4.3^20. 8^9}/{5.2^10. 6^19-7.2^29. 27^6}`

`B={5.(2^2)^15 . (3^2)^9 - 2^2 . 3^20 . (2^3)^9}/{5.2^10 . (2.3)^19 - 7.2^29 . (3^3)^6}`

`B={5.2^30 . 3^18-2^2 . 3^20 . 2^27}/{5.2^10 . 2^19 . 3^19 - 7.2^29 . 3^18}`

`B={5.2^30 . 3^18-2^29 . 3^20}/{5 . 2^29 . 3^19-7 . 2^29 . 3^18}`

`B={2^29 . 3^18 . (5.2-3^2)}/{2^29 . 3^18 . (5.3-7)}`

`B={2^29 . 3^18 .(10-9)}/{2^29 . 3^18 . (15-7)}`

`B={10-9}/{15-7}`

`B=1/8`

`-` Vậy : `B=1/8 .`

`C=1+3^2+3^4+3^6+...+3^2022`

`3^2C=3^2+3^4+3^6+3^8+...+3^2024`

`9C-C=(3^2+3^4+3^6+3^8+...+3^2024)-(1+3^2+3^4+3^6+...+3^2022)`

`8C=3^2024-1`

`C={3^2024-1}/8`

`-` Vậy : `C={3^2024-1}/8 .`

`2)`

`a)x:(9 1/2-3/2)={0,4+2/9-2/11}/{1,6+8/9-8/11}`

`x:(19/2-3/2)={2/5+2/9-2/11}/{8/5+8/9-8/11}`

`x : 16/2={2(1/5+1/9+1/11)}/{8(1/5+1/9-1/11)}`

`x : 8=2/8`

`x=2/8xx8`

`x=16/8`

`x=2`

`-` Vậy : `x=2.`

`b)(2x-15)^5=(2x-15)^3`

`(2x-15)^5-(2x-15)^3=0`

`(2x-15)^3[(2x-15)^2-1]=0`

`+)TH1:`

`(2x-15)^3=0`

`2x-15=0`

`2x=0+15`

`2x=15`

`x=15:2`

`x=7,5`

`+)TH2:`

`(2x-15)^2-1=0`

`(2x-15)^2=0+1`

`(2x-15)^2=1`

`=>` \(\left[ \begin{array}{l}(2x-15)^2=1^2\\(2x-15)^2=(-1)^2\end{array} \right.\)

`=>` \(\left[ \begin{array}{l}2x-15=1\\2x-15=-1\end{array} \right.\)

`=>` \(\left[ \begin{array}{l}2x=1+15\\2x=-1+15\end{array} \right.\)

`=>` \(\left[ \begin{array}{l}2x=16\\2x=14\end{array} \right.\)

`=>` \(\left[ \begin{array}{l}x=16:2\\x=14:2\end{array} \right.\)

`=>` \(\left[ \begin{array}{l}x=8\\x=7\end{array} \right.\) 

`-` Vậy : `x∈{7,5;8;7}`

`#Sal_tSea`