Limits and continuity

Practice sheet

Fresh questions from the whole chapter, to do on paper.

To save a PDF, choose “Save as PDF” in the print dialog.

  1. f(x)=x2−36x−6f(x) = \dfrac{x^2 - 36}{x - 6} is not defined at x=6x = 6. What value does f(x)f(x) approach as x→6x \to 6?
  2. f(x)=(x−p)(x+4)x−pf(x) = \dfrac{(x - p)(x + 4)}{x - p} for p=0p = 0: its graph is the line y=x+4y = x + 4 with a hole. Tap the point the graph approaches as x→0x \to 0.
  3. f(x)=x2f(x) = x^2 for x≠4x \ne 4, and f(4)=33f(4) = 33. What is lim⁡x→4f(x)\displaystyle\lim_{x \to 4} f(x)?
    1. 1616
    2. 3333
    3. It does not exist
  4. Find lim⁡x→7x2−15x+56x−7\displaystyle\lim_{x \to 7} \dfrac{x^2 - 15x + 56}{x - 7}.
  5. Find lim⁡h→0(8+h)2−64h\displaystyle\lim_{h \to 0} \dfrac{(8 + h)^2 - 64}{h}.
  6. Find lim⁡x→9x−3x−9\displaystyle\lim_{x \to 9} \dfrac{\sqrt{x} - 3}{x - 9}.
  7. f(x)={x+6if x<52xif x≥5f(x) = \begin{cases} x + 6 & \text{if } x < 5 \\ 2x & \text{if } x \ge 5 \end{cases}. What is lim⁡x→5f(x)\displaystyle\lim_{x \to 5} f(x)?
    1. It does not exist: the left and right limits differ
    2. 1111
    3. 1010
  8. Find lim⁡x→0−∣3x∣x\displaystyle\lim_{x \to 0^-} \dfrac{|3x|}{x}.
  9. Find lim⁡x→0sin⁡(6x)x\displaystyle\lim_{x \to 0} \dfrac{\sin(6x)}{x}.
  10. Find lim⁡x→0sin⁡(3x)sin⁡(9x)\displaystyle\lim_{x \to 0} \dfrac{\sin(3x)}{\sin(9x)}.
  11. What is lim⁡x→0x2sin⁡(1x)\displaystyle\lim_{x \to 0} x^{ 2 }\sin\left(\dfrac{1}{x}\right)?
    1. 0, by the squeeze theorem
    2. It does not exist, because sin⁡(1/x)\sin(1/x) oscillates
    3. 1
  12. Find lim⁡x→∞4x2+15x2+4\displaystyle\lim_{x \to \infty} \dfrac{ 4x^2 + 1}{ 5x^2 + 4}.