Where did the minus come from?

[agile marlin]

In general, $\sqrt{x^2}=|x|$. So, we can say that $\sqrt{(x-1)^2}=|x-1|$. \ \ However, as we approaching $x=1$ from the negative direction, $x-1<0 \implies |x-1|=-(x-1)$.

[mystic maple]

Civil Service Pigeon

[wintry snow]

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