Chung minh: ║ ║x ║- ║y ║ ║ ≤ ║x-y ║
║la gia tri tuyet doi
║ ║la gia tri tuyet doi cua gia tri tuyet doi
Chung minh: ║ ║x ║- ║y ║ ║ ≤ ║x-y ║ ║la gia tri tuyet doi ║ ║la gia tri tuyet doi cua gia tri tuyet doi
By Vivian
By Vivian
Chung minh: ║ ║x ║- ║y ║ ║ ≤ ║x-y ║
║la gia tri tuyet doi
║ ║la gia tri tuyet doi cua gia tri tuyet doi
Ta có:
$| |x| – |y| | ≤ |x-y|$
$⇔ |x – y| ≤ |x-y|$
$⇔ |x – y| = |x-y|
$⇔ | |x| – |y| | ≤ |x-y|$
║ ║x ║- ║y ║ ║ ≤ ║x-y ║
<=> ║ x – y ║ ≤ ║x-y ║
<=> ║ x – y ║ = ║x-y ║
=> ║ ║x ║- ║y ║ ║ = ║x-y ║