Spivak Calculus Chapter 1 Problem 5 (ii)

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Prove : If $a < b$ then $-b < -a$

My proof :

$a + (-b) < b + (-b) $

$a - b < 0$

$a - b + (-a) < 0 + (-a)$

$a + (-a) -b < -a$

$-b < -a$

Is my proof correct?

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Direct alternative proof.
$a < b $
$-a + a - b < -a + b - b $
$-b < -a$