Counter Examples

Mathematics Dictionary
Dr. K. G. Shih

Contents of Mathematics Dictionary

Program WebABC Applications of Mathematics Dictionary on Internet

Graphic Samples of Mathematics Dictinary

Subject : Intersection of Linear Function with its Inverse

Q1. What is the inverse of a function
A1. The defintion is
    * It is the reflection of Y = F(X) about Y = X
    * It is the image of Y = F(X) about Y = X
    * Function y = x looks like an mirror

Q2. Expression of inverse of y = F(x) = a*x+b
A2. Inverse of Y = a*x+b is X = a*y+b
    * Solve for x and we have x = (y-b)/a
    * Interchange x and y we have * The inverse is y = (x-b)/a
    * Express x in terms of y * The inverse is x = a*y + b

Q3. Proof inverse is x=a*y + b
A3. Proof
    * Since y = (x-b)/a
    * Hence x-b = a*y
    * Hence x = a*y+b

Q4. Properties of inverse function
A4. Let y=F(x) and inverse y=G(x)
    * F(G(x)) = x
    * G(F(x)) = x

Q5. Example : Prove F(G(x))=x
A5. Proof
    * F(x) = a*x+b and G(x) = (x-b)/a
    * F(G(x))=a*(G(x))+b
    * F(G(x))=a*((x-b)/a) + b = x

Q6. How How many intersctions of y = a*x+b with its inverse

A6. Graphic solutions Program ABH
    * There is no intersection
    * There is one intersection

Q7. How to find intersections ?
A7. Find intersection of y = a*x + b with inverse
    * If function has intersection with its inverse
    * It must intersect with y=x
    * Hence we solve y = a*x + b and y = x first
    * This gives a quadratic equation : a*x + b = x

Q8. When is there no intersection ?
A8. Answer
    * If y=x+b or y=x-b there is no intersection
    * Since the line is parallel to y=x

Examples
Example 1 : Use Program ABH to view the diagrams
    * y = 2*x + 3
    * y = 2
    * x = 2

Remarks
    * The author spent more than 10 years to compile Math Dictionary
    * The system is easy in use and gives thousands applications
    * On this website only some samples are given for demonstration
    * You should have it on your computer
    * Then you can use your computer as a graphic calculator

    * Also you can find many mathematical patterns for school wook
    * For more information, Please contact Dr. K. G. Shih
    * Visit the URL to see more samples
    * Visit the URL to view 105 graphic samples in Program WebABC
    * You can download it and Click file WebABC will run


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