a, a-5 ≥ b-5
=> a-5+5 ≥ b-5+5
=> a ≥ b
b) 15 + a ≤ 15 + b
=> 15+a-15 ≤ 15+b-15
=> a ≤ b
a) Vì a - 5 ≥ b - 5 => a - 5 + 5 ≥ b - 5 + 5
=> a ≥ b
b) Vì 15 + a ≤ 15 + b => 15 + a -15 ≤ 15 + b -15
=> a ≤ b
a)
+) Nếu "=" nhau
<=> a - 5 = a - 5 => a = b
+) Nếu ">"
<=> a - 5 > b - 5 => a > b
b)
+) Nếu "=" nhau
<=> 15 + a = 15 + b => a = b
+) Nếu "<"
<=> 15 + a < 15 + b => a < b
Vậy.....
a) ta có: \(a-5\ge b-5\)
\(\Rightarrow a\ge b-5+5\)
\(\Rightarrow a\ge b\)
b) ta có: \(15+a\le15+b\)
\(\Rightarrow a\le15+b-15\)
\(\Rightarrow a\le b\)