Thursday, 7 March 2013

calculus - The limit of this function as x approaches 2 from the positive direction (the right).




lim




Am I correct in thinking the limit does not exist? Since as x approaches 2 from the right the function increases to infinity and a limit cannot equal infinity. Thanks!


Answer




\lim_{x\rightarrow 2^+} \frac{\sqrt{x^2-4}}{x-2}=\lim_{x\rightarrow 2^+}\frac{\sqrt{(x-2)(x+2)}}{x-2}=\lim_{x\rightarrow 2^+}\frac{\sqrt{(x-2)}\sqrt{(x+2)}}{x-2}=\lim_{x\rightarrow 2^+}\frac{\sqrt{(x+2)}}{\sqrt{(x-2)}}



Then as you said the denominator tends to 0^+ and hence the whole limit tends to +\infty


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