Đáp án:
Câu `2:`
`a,` `4(3x-4)-2=18`
`<=>` `4(3x-4)=20`
`<=>` `3x-4=5`
`<=>` `3x=9`
`<=>` `x=3`
Vậy `x=3`
`b,` `B={x\inNN|30<x<=40}`
`<=>` `B={31;32;33;...;40}`
Vậy `B={31;32;33;...;40}`
`c,` `(105-x):2^5=3^0+1`
`<=>` `(105-x):2^5=2`
`<=>` `105-x=64`
`<=>` `x=41`
Vậy `x=41`
`d,` `2x-138=2^2 .3^2`
`<=>` `2x-138=36`
`<=>` `2x=174`
`<=>` `x=87`
Vậy `x=87`
`e,` `(6x-39).28=5628`
`<=>` `6x-39=201`
`<=>` `6x=240`
`<=>` `x=40`
Vậy `x=40`
`f,` `(9x+2).3=60`
`<=>` `9x+2=20`
`<=>` `9x=18`
`<=>` `x=2`
Vậy `x=2`
`g,` `(26-3x):5+71=75`
`<=>` `(26-3x):5=4`
`<=>` `26-3x=20`
`<=>` `3x=6`
`<=>` `x=2`
Vậy `x=2`
`h,` `5^(x+1)=125`
`<=>` `5^(x+1)=5^3`
`<=>` `x+1=3`
`<=>` `x=2`
Vậy `x=2`
