Bài `1 :`
`d) 2^4 . 5 - [ 131 - ( 13 - 4 )^2 ]`
`= 80 - ( 131 - 81 )`
`= 80 - 50`
`= 30`
`e) 500 - {5[409 - ( 2^3 . 3 - 21)^2] - 1724}`
= 500 - [5( 409 - 9) - 1724]`
`= 500 - (5 . 400 - 1724 )`
`= 500 - 276`
`= 225`
Bài `2 :`
`a) ( x - 17 ) . 200 = 400`
`=> x - 17 = 400 : 200 = 2`
`=> x = 2 + 17`
=> x = 19`
`b) ( x-105) : 21 = 15`
`=> x - 105 = 315`
`=> x = 105 + 315`
`=> x = 420`
`c) 541 + ( 128 - x ) = 735`
`=> 128 -x = 735 - 541`
`=> 128 - x = 194`
`=> x = 128 - 194 `
Vì` 128 - 194 < 0 nên ( 128 - 194 ) ∉ N`
Vì `x \in NN` nên `x = ∅`
`d) 24 + 5x = 7^5 : 7^3`
`=> 24 + 5x = 7^2 = 49`
`=> 5x = 49 - 24 = 25`
`=> x = 25 : 5 = 5`
`e) 5^{2x-3} - 2 . 5^2 = 5^2 . 3`
`=> 5^{2x-3} - 2 = 3`
`=> 5x^{2x-3} = 1`
`=> 5x^{2x-3} = 5^0`
`=> 2x - 3 = 0`
`=> 2x = 3 `
`=> x = 3/2`
Vì `x \in NN` nên` x = ∅`
