Calculus question about arc length? (Solved - thank you).

I’m confused about one little part of the arc length topic in Calculus.

The question is:

y = 4 - 3x on [-3,2] (Use calculus.)

The answer and the steps given are as follows:

I’m just confused on the last step. How does sqrt(10)dx become 5(sqrt10). Without knowing this I can’t answer any of the questions on this topic.

Its probably something really obvious, but I can’t see it.


Six months ago… 

Montgomery Scott wasn’t the sort of man to notice a woman. Indeed, many might have called him ignorant to any casual advances that had been made by some of the officers on board who had found Olson’s replacement to be … well, interesting to say the very least. On the whole, however, the tended to ignore him as much as he did them, finding his love for The Enterprise to be a little too weird for their liking. Many suspected that he might actually have some sort of thing for the advanced vessel, given the way that he often ‘spoke’ to it, or was found stroking the bulkhead when he thought no one was looking. It was thought - even by Scott himself - that he was likely to spend the rest of his days as a bachelor. Any previous attempts at relationships had inevitably crashed and burned as soon as his idiosyncrasies became apparent. He wasn’t unhappy as such. To work upon such a magnificent ship was a dream come true, and for the most part the chief engineer was content. That was, until he saw her. 

It had been an evening like any else. The Enterprise was on a small recon mission to Delta IV; the warp core running beautifully as they sailed along casually at Warp-5. Scotty was doing his usual rounds, monitoring the core with the attentiveness of a parent, ready to act should anything go awry. He caught a glimpse of her out of the corner of his eye at first, just a silhouette against the bright light of the outer hallway. At first, he assumed it to be just another engineer doing their Beta shift rounds, until he noticed the blue uniform in the half-light. Medical? What was someone from medical doing in engineering? Were they lost? She stopped for but a moment, glancing up momentarily, her blonde waves falling gently around her face. He went to speak but his voice caught as he felt his pulse quicken, and an unusual sensation come over him; almost like a kind of déja vú. He knew this woman… yet how was a mystery. He very rarely spoke to anyone outside of engineering. Yet he knew her as though she had walked right out of a memory… 

One furtive glance behind her and she was gone, leaving the chief engineer to marvel in this unfathomable sensation. Who was she, and why did he know her face?? Rushing to a nearby terminal, he began a thorough search of all medical personnel aboard the ship, hoping to catch a glance of his mystery medical officer. It was a good forty minutes before he managed to find her; Dr. Briar Roan, an exobiology expert from hydroponics. He stared at the picture, a wave of nostalgia washing over him he read the name, his pulse quickening once more. It was so long ago; almost twenty-five years and yet there she was; older yes, but still as beautiful as he remembered. “Oh my God… Bee…?”