Question

[Lê Hoàng Khánh]

9. Tìm x, y biết.

a) |x-2|+|2x+y|≤0

b) |x-2|+|x-5|≤3

Answer 1

[ILoveMath]

a) |x-2|+|2x+y|≤0

|x-2| ≥ 0

|2x+y|≥ 0

mà |x-2|+|2x+y|≤0⇒|x-2|+|2x+y|=0

⇒|x-2|=0⇒x=2

|2x+y|=0⇒|2.2+y|=0⇒|4+y|=0⇒y=-4

vậy (x,y)={(2;-4)}