HOME  |  WHAT'S NEW  |  CART  |  FIND:   |  HELP

utf05-005

For each below do the following: Compute the limits, write in words what techniques you used to solve them, then write another limit of the same type. \begin{alignat*}{2} a)   &\lim_{x \to 1}\frac{x^3-x^2+x-1 }{ x^2-1} &             &\lim_{x\to 0}\frac{(1+x)^2-1 }{ (1+x)^3 - 1} \\ b)   &\lim_{x \to 4}\frac{\root \uproot 3 3 \of {x} - \root \uproot 3 3 \of {4} }{ x-4} &             &\lim_{x \to 0}\frac{(x-2) + 2 }{ {\root \uproot 3 3 \of {x-2} + \root \uproot 3 3 \of {2}}} \\ c)   &\lim_{x \to 3}\frac{2x^3-18x^2+54x-54 }{ x-3} &             &\lim_{x \to -1}\frac{x^4+ 4x^3+6x^2+4x+1 }{ (x^2-1)^4} \\ d)   &\lim_{x \to 3}\frac{\sqrt x - \sqrt 3 }{ x-3} &             &\lim_{x \to 0}\frac{x^2 }{ 1 - \sqrt {1-x^2}} \\ e)   &\lim_{x \to a}\frac{|x-a| }{ x-a} &             &\lim_{x \to -3^{-}}\frac{|x+3| }{ x+3} \\ f)   &\lim_{x \to 1}\frac{\root 3 \of x - 1 }{ x-1} &             &\lim_{x \to 1}\frac{\root 4 \of x -1 }{ x-1} \\ g)   &\lim_{x \to 2} f( x),     \lim_{x \to 2^{-}} f( x),    \lim_{x \to 2^{+}} f( x) &             & \text{where}    f( x) = \begin{cases} x^2,&   x \geq 2 \\ \frac{x^2-4 }{ x-2},&   x<2 \end{cases} \end{alignat*}


Tags: limits, indeterminate-forms, one-sided-limits, rational, root, composite, piecewise-defined, absolute-value, creating-examples, tricks, rote-problem, a--v--a, t2, c1
At first glance, this seems to be a limit problem gone mad, but it was written with specific goals I mind. In the context of calculating limits with indeterminate forms we review some intensive algebra. Many calculus students seem to have weak algebra skills and don’t easily recognize places where simple factoring . This is an exercise in factoring - getting students to solidify vague recollections of differences of squares or cubes, etc. It’s a chance to ask, “When working with polynomials, what information does f(a)=0 give us?” All these limits have indeterminate form 0/0.

James Epperson 1998-08-09