Question

Bài 5 : so sánh a và b nếu a) a - 10 > b - 10 c) - a - 9 >= - b - 9 e) - 4a + 9 < -4b + 9 b) 25 + a > 25 + b f) - 5a - 6 2b - 5

Answer 1

a)

`a-10>b-10`

`<=>a-10+10>b-10+10`

`<=>a>b`

c)

`-a-9≥-b-9`

`<=>-a-9+9≥-b-9+9`

`<=>-a≥-b`

`<=>-a*(-1)/1≤-b*(-1)/1`

`<=>a≤b`

e)

`-4a+9< -4b+9`

`<=>-4a+9-9< -4b+9-9`

`<=>-4a< -4b`

`<=>-4a*(-1)/4> -4b*(-1)/4`

`<=>a>b`

b)

`25+a>25+b`

`<=>25+a-25>25+b-25`

`<=>a>b`

f)

cái giữa là dấu gì vậy ạ

Answer 2

\(a,a-10>b-10\)

\(\Rightarrow a-10+10>b-10+10\)

\(\Leftrightarrow a>b\)

\(b,-a-9\ge-b-9\)

\(\Rightarrow-a-9+9\ge-b-9+9\)

\(\Leftrightarrow-a\ge-b\)

\(c,-4a+9< -4b+9\)

\(\Rightarrow-4a+9-9< -4b+9-9\)

\(\Leftrightarrow a< b\)

\(d,25+a>25+b\)

\(\Rightarrow25+a-25>25+b-25\)

\(\Leftrightarrow a>b\)

Câu cuối thiếu dấu bạn ơi!