Đáp án:
Giải thích các bước giải:
`4A`
`a) -(59-3x)+39=3x-20`
`VT = -(59-3x)+39=-59+3x+39=3x-20=VP`
`=> VT=VP (đpcm)`
`b)`
Sửa đề `1-c-2a`
`-(a+b+c)+(b-c)-(a-c-1)=1-c-2a`
`VT=-(a+b+c)+(b-c)-(a-c-1)`
`=-a-b-c+b-c-a+c+1`
`=(-a-a)+(b-b)+(c-c-c)+1`
`=1-c-2a=VP`
`=> VT=VP (đpcm)`
`4B`
`a) -(19-2x)+39=2x+20`
`VT=-(19-2x)+39=-19+2x+39=2x+20=VP`
`=> VT=VP (đpcm)`
`b)`
Sửa đề : `-c-2a-1`
`-(a+b+c)+(b-c)-(a-c+1)=c-2a-1`
`VT=-(a+b+c)+(b-c)-(a-c+1)`
`=-a-b-c+b-c-a+c-1`
`=(-a-a)+(b-b)-(c+c-c)-1`
`=-2a-c-1=VP`
`=> VT=VP (đpcm)`
