Question

Help me pờ li !!! En thank kiu sâu mắc!?!!!!!!

Answer 1

$a)a>b\\\to -a<-b\\\to -3a<-3b\\\to -3a-3<-3b-3(đpcm)\\b-2x-3<-2y-3\\\to -2x<-2y\\\to -x<-y\\\to x>y$

Answer 2

`c)(a-b)x<5(a-b)`

`<=>(a-b)x-5(a-b)<0`

`<=>(a-b)(x-5)<0`

Vì `x<5=>x-5<0`

`=>a-b>0`

`<=>a>b`

`d)(a-b)x<2(a-b)`

`<=>(a-b)x-2(a-b)<0`

`<=>(a-b)(x-2)<0`

Vì `x>2=>x-2>0`

`=>a-b<`

`<=>a<b`

Answer 3

Bài 1:

a) Ta có: -3a-3<-3b-3

\(\Leftrightarrow-3a< -3b\)

nên a>b

b) Ta có: \(-2x-3< -2y-3\)

\(\Leftrightarrow-2x< -2y\)

nên x>y

Answer 4

Bài 1: 

c) Ta có: (a-b)x<5(a-b)

\(\Leftrightarrow\left(a-b\right)x-5\left(a-b\right)< 0\)

\(\Leftrightarrow\left(a-b\right)\left(x-5\right)< 0\)

mà x-5<0

nên a-b>0

hay a>b