View Full Version : How about this limit?
Thanks...
Evaluate the limit
lim x->-1 (2x^2-x-3)/(x+1)
I simplified to (2x^2-3)/(2x+1) = -1/-1 = 1
Is this correct?
Zorodius
Jun4-04, 06:42 PM
I believe you want to factor the top, cancel out the hole in the graph, and then evaluate by substitution.
\lim_{x\rightarrow -1} \frac {2x^2-x-3}{x+1}
= \lim_{x\rightarrow -1} \frac {(2x-3)(x+1)}{x+1}
= \lim_{x\rightarrow -1} 2x-3
= -5.
You can use L'Hospital's rule:
\lim_{x\rightarrow -1} \frac {2x^2-x-3}{x+1}
If you plug in, you get 0/0, so:
\lim_{x\rightarrow -1} \frac {2x^2-x-3}{x+1}
= \lim_{x\rightarrow -1} \frac {4x-1}{1}
Plug in and you get -5.
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