Math Problem Statement

Find the indicated quantities for f(x) = 3x^2. (A) The slope of the secant line through the points (1, f(1)) and (1 + h, f(1 + h)), h ≠ 0. (B) The slope of the graph at (1, f(1)). (C) The equation of the tangent line at (1, f(1)).

Solution

Let's break down the problem and solve it step by step.

We are given the function f(x)=3x2f(x) = 3x^2, and we need to find:

(A) The slope of the secant line through the points (1,f(1))(1, f(1)) and (1+h,f(1+h))(1 + h, f(1 + h)), where h0h \neq 0.

The slope of the secant line is given by: msecant=f(1+h)f(1)(1+h)1m_{\text{secant}} = \frac{f(1 + h) - f(1)}{(1 + h) - 1} First, calculate f(1)f(1) and f(1+h)f(1 + h): f(1)=3(12)=3f(1) = 3(1^2) = 3 f(1+h)=3(1+h)2=3(1+2h+h2)=3+6h+3h2f(1 + h) = 3(1 + h)^2 = 3(1 + 2h + h^2) = 3 + 6h + 3h^2 Now substitute these into the formula for the secant slope: msecant=(3+6h+3h2)3h=6h+3h2h=6+3hm_{\text{secant}} = \frac{(3 + 6h + 3h^2) - 3}{h} = \frac{6h + 3h^2}{h} = 6 + 3h Thus, the slope of the secant line is: msecant=6+3hm_{\text{secant}} = 6 + 3h

(B) The slope of the graph at (1,f(1))(1, f(1)).

The slope of the graph at a point is the derivative of the function evaluated at that point. First, find the derivative of f(x)f(x): f(x)=ddx(3x2)=6xf'(x) = \frac{d}{dx}(3x^2) = 6x Now, evaluate the derivative at x=1x = 1: f(1)=6(1)=6f'(1) = 6(1) = 6 So, the slope of the graph at (1,f(1))(1, f(1)) is: m=6m = 6

(C) The equation of the tangent line at (1,f(1))(1, f(1)).

The equation of the tangent line is given by the point-slope form: yf(1)=m(x1)y - f(1) = m(x - 1) We already know that f(1)=3f(1) = 3 and m=6m = 6, so the equation becomes: y3=6(x1)y - 3 = 6(x - 1) Simplifying: y=6x6+3y = 6x - 6 + 3 y=6x3y = 6x - 3 Thus, the equation of the tangent line is: y=6x3y = 6x - 3


Let me know if you'd like further clarifications or details!

Here are 5 related questions to think about:

  1. What would the slope of the secant line be if h0h \to 0?
  2. How would the derivative change if the function were f(x)=3x3f(x) = 3x^3?
  3. What is the general formula for the slope of the tangent line at any point x=ax = a?
  4. How would you calculate the second derivative of f(x)=3x2f(x) = 3x^2?
  5. What does the tangent line represent geometrically?

Tip:

The slope of the secant line gives an average rate of change, while the tangent line gives the instantaneous rate of change at a specific point.

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Math Problem Analysis

Mathematical Concepts

Algebra
Calculus
Derivatives
Tangents

Formulas

Slope of secant line: m_secant = (f(1 + h) - f(1)) / ((1 + h) - 1)
Derivative: f'(x) = 6x
Point-slope form of a line: y - f(x1) = m(x - x1)

Theorems

Derivative of a function
Tangent line at a point

Suitable Grade Level

Grades 10-12