Math Problem Statement

What is the equation of the tangent line to f at a using definition of limit?

What is the equation of the tangent line to f at a using definition of limit?

Solution

The expression in the image you provided is the derivative of a function f(x)f(x) at a point aa using the definition of the derivative:

f(a)=limh021+h2hf'(a) = \lim_{h \to 0} \frac{\frac{2}{1+h} - 2}{h}

This appears to represent the derivative of the function f(x)=2xf(x) = \frac{2}{x}, evaluated at a=1a = 1, based on the structure of the difference quotient. Let's verify this and then find the equation of the tangent line.

Step-by-step Solution:

1. Find the derivative f(1)f'(1)

We are given the limit expression:

f(1)=limh021+h2hf'(1) = \lim_{h \to 0} \frac{\frac{2}{1+h} - 2}{h}

Simplify the numerator: 21+h2=22(1+h)1+h=222h1+h=2h1+h\frac{2}{1+h} - 2 = \frac{2 - 2(1+h)}{1+h} = \frac{2 - 2 - 2h}{1+h} = \frac{-2h}{1+h}

Now, substitute this into the limit expression: f(1)=limh02h1+hhf'(1) = \lim_{h \to 0} \frac{\frac{-2h}{1+h}}{h}

Simplify further: f(1)=limh02hh(1+h)=limh021+hf'(1) = \lim_{h \to 0} \frac{-2h}{h(1+h)} = \lim_{h \to 0} \frac{-2}{1+h}

As h0h \to 0, this becomes: f(1)=21+0=2f'(1) = \frac{-2}{1+0} = -2

2. Equation of the tangent line at x=1x = 1

The equation of the tangent line at a point (a,f(a))(a, f(a)) is given by the point-slope form: yf(a)=f(a)(xa)y - f(a) = f'(a)(x - a)

We know that f(x)=2xf(x) = \frac{2}{x}, so: f(1)=21=2f(1) = \frac{2}{1} = 2 And we already found that f(1)=2f'(1) = -2. Therefore, the equation of the tangent line is: y2=2(x1)y - 2 = -2(x - 1) Simplifying: y2=2x+2y - 2 = -2x + 2 y=2x+4y = -2x + 4

Conclusion:

The equation of the tangent line to the curve f(x)=2xf(x) = \frac{2}{x} at x=1x = 1 is: y=2x+4y = -2x + 4

Would you like more details on any part of the process?

Follow-up Questions:

  1. What is the geometric meaning of a derivative at a point?
  2. How would the tangent line change for other values of aa?
  3. Can you find the second derivative of f(x)=2xf(x) = \frac{2}{x}?
  4. What does the derivative of f(x)f(x) tell you about the concavity of the function?
  5. How does the point-slope form of a line relate to the derivative of a function?

Tip:

When simplifying limits, always check if you can cancel common terms before directly evaluating the limit.

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Math Problem Analysis

Mathematical Concepts

Calculus
Derivatives
Limits
Tangent Line

Formulas

f'(a) = lim (h -> 0) [(f(a+h) - f(a)) / h]
Point-Slope Form: y - f(a) = f'(a)(x - a)

Theorems

Definition of the Derivative
Limit Laws

Suitable Grade Level

Grades 10-12 (High School Calculus)