How to show non-negative tangents ?

  • Thread starter ghostanime2001
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In summary, we are given two problems: one to show that there are no tangents with negative slope to the graph of f(x)=\frac{5x+2}{x+2}, and the other to determine the equation of the tangent to the curve y=\frac{x^{2}-1}{3x} at x=2. The first problem does not allow the use of quotient rule, but suggests using the product rule with the chain rule or polynomial division. The second problem requires three pieces of information for a tangent, and solving f(x)<0 will not give the desired result. Instead, we need to show that the derivative of the function is never negative.
  • #1
ghostanime2001
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Homework Statement


1. Show that there are no tangents to the graph of [tex]f(x) = \frac{5x+2}{x+2}[/tex] that have a negative slope.

2. Determine the equation of the tangent to the curve [tex]y = \frac{x^{2}-1}{3x}[/tex] at x = 2

Homework Equations


1. Our teacher told us not to use the quotient rule because it is not in our curriculum so please do not give me a solution using the quotient rule. Thanks.
 
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  • #2
What about using the product rule with the chain rule then? Use the fact that A/B=AB-1.
 
  • #3
1. Or Perform Polynomial division on f(x), then its quite simple.

2. You need 3 pieces of information for a tangent - what are they?
 
  • #4
for 1. don't i use inequality ? set the equation f(x) < 0 and solve for x if it can't be solved then u can conclude there are no points that can give me a negative tangent
 
  • #5
ghostanime2001 said:
for 1. don't i use inequality ? set the equation f(x) < 0 and solve for x if it can't be solved then u can conclude there are no points that can give me a negative tangent

If you solve f(x)<0, you will be finding all x for which the function itself is negative i.e. below the x axis. But that's not what you want to find, you need to show that the DERIVATIVE is never negative.
 

1. What does it mean for a tangent to be non-negative?

When we talk about tangents in mathematics, we are referring to the slope of a line that touches a curve at a specific point. The slope of a tangent can be positive, negative, or zero. A non-negative tangent simply means that the slope is either positive or zero, but not negative.

2. Why is it important to show non-negative tangents?

In many applications of mathematics, such as optimization problems, it is important to know the direction of change at a specific point. By showing that the tangent is non-negative, we can determine that the function is increasing or staying constant at that point.

3. How can we determine if a tangent is non-negative?

To determine if a tangent is non-negative, we need to find the derivative of the function at the given point. If the derivative is greater than or equal to zero, then the tangent is non-negative. If the derivative is negative, then the tangent is negative.

4. Can a tangent be both non-negative and negative?

No, a tangent can only be either non-negative or negative at a given point. This is because the slope of a tangent is determined by the derivative of the function at that point, and the derivative can only have one value at a specific point.

5. How can we use non-negative tangents in real-world problems?

Non-negative tangents can be useful in many real-world applications, such as determining the maximum or minimum value of a function, finding the best rate of change, or optimizing a process. By understanding the direction of change at a specific point, we can make informed decisions and solve problems more efficiently.

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