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This text discusses the concept of limits in calculus, particularly as a variable approaches specific values. It illustrates how to evaluate limits via substitution, understanding discontinuities, and applying L'Hospital's Rule when applicable. Key concepts include recognizing when a function's graph has discontinuities, such as jump discontinuities or vertical asymptotes. Furthermore, it provides examples and practice questions to reinforce understanding of these mathematical concepts, making it easier for students to grasp limits and their implications in function behavior.
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As x approaches 3 from both directions, y approaches 8 We can find the limit by substituting x = 3 into the equation
Practice Answer: The limit is 24
When we try to substitute into we get which is undefined. If we draw the graph we find that we get a straight line with equation
The hole in the graph at x = 1 is a discontinuity.y has a value for every x except x = 1. i.e.
You can recognise a discontinuity because you need to lift your pen to continue your graph. The graph below is continuous because we can draw it without having to lift the pen.
Although , we do have a limit at x = 1.
Two methods to find the limit.Method 1 Now substitute x = 1 to get a limit of 2 i.e.
Method 2Use L’Hospital’s Rule Note: Only use this when substitution gives 0/0
Practice Answer: Substituting gives Using either factorising or L’Hospital’s Rule: Limit is
The graph is not heading towards the same value so there is no limit. Tends towards 1 Tends towards -1
More Limits Divide top and bottom by x