Bài 14 : Cho A = a+b+3 B = b+c-1 C = b-c+4 D = -(b-a) Chứng tỏ : A – B = C + D 21/11/2021 Bởi Madelyn Bài 14 : Cho A = a+b+3 B = b+c-1 C = b-c+4 D = -(b-a) Chứng tỏ : A – B = C + D
Thay `A = a+b+3;B = b+c-1` `→A-B=(a+b+3)-(b+c-1)` `=a+b+3-b-c+1` `=a+(b-b)-c+(3+1)` `=a-c+4` Thay `C = b-c+4;D=-(b-a)=-b+a` `→C+D=b-c+4-b+a` `=(b-b)-c+a+4` `=a-c+4` `→A-B=C+D` (đpcm) Vậy `A-B=C+D` Bình luận
Thay `A = a+b+3;B = b+c-1`
`→A-B=(a+b+3)-(b+c-1)`
`=a+b+3-b-c+1`
`=a+(b-b)-c+(3+1)`
`=a-c+4`
Thay `C = b-c+4;D=-(b-a)=-b+a`
`→C+D=b-c+4-b+a`
`=(b-b)-c+a+4`
`=a-c+4`
`→A-B=C+D` (đpcm)
Vậy `A-B=C+D`