Math Problem Statement

Find the indicated quantities for 𝑓(π‘₯) = 3π‘₯ 2 (A) The slope of the secant line through the points (2, f (2)) and (5, f (5)) on the graph of y = f (x). (B) The slope of the secant line through the points (2, f (2)) and (2 + h, f (2 + h)), h β‰  0. Simplify your answer. (C) The slope of the graph at (2, f (2)).

Solution

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

(A) The slope of the secant line through the points (2,f(2))(2, f(2)) and (5,f(5))(5, f(5)) on the graph of y=f(x)y = f(x).

(B) The slope of the secant line through the points (2,f(2))(2, f(2)) and (2+h,f(2+h))(2 + h, f(2 + h)), where h≠0h \neq 0, and we need to simplify the answer.

(C) The slope of the graph at (2,f(2))(2, f(2)), which is the derivative of f(x)f(x) evaluated at x=2x = 2.

Solution:

(A) The slope of the secant line through (2,f(2))(2, f(2)) and (5,f(5))(5, f(5)):

The slope of a secant line between two points (x1,f(x1))(x_1, f(x_1)) and (x2,f(x2))(x_2, f(x_2)) is given by the formula:

m=f(x2)βˆ’f(x1)x2βˆ’x1m = \frac{f(x_2) - f(x_1)}{x_2 - x_1}

Here, x1=2x_1 = 2 and x2=5x_2 = 5. Let's calculate f(2)f(2) and f(5)f(5):

f(2)=3(2)2=3Γ—4=12f(2) = 3(2)^2 = 3 \times 4 = 12 f(5)=3(5)2=3Γ—25=75f(5) = 3(5)^2 = 3 \times 25 = 75

Now, apply the slope formula:

m=f(5)βˆ’f(2)5βˆ’2=75βˆ’123=633=21m = \frac{f(5) - f(2)}{5 - 2} = \frac{75 - 12}{3} = \frac{63}{3} = 21

So, the slope of the secant line is 21.

(B) The slope of the secant line through (2,f(2))(2, f(2)) and (2+h,f(2+h))(2 + h, f(2 + h)), where h≠0h \neq 0:

The slope of the secant line in this case is:

m=f(2+h)βˆ’f(2)(2+h)βˆ’2=f(2+h)βˆ’f(2)hm = \frac{f(2 + h) - f(2)}{(2 + h) - 2} = \frac{f(2 + h) - f(2)}{h}

We already know that f(2)=12f(2) = 12. Now, we need to calculate f(2+h)f(2 + h):

f(2+h)=3(2+h)2=3(4+4h+h2)=12+12h+3h2f(2 + h) = 3(2 + h)^2 = 3(4 + 4h + h^2) = 12 + 12h + 3h^2

Now, substitute this into the slope formula:

m=(12+12h+3h2)βˆ’12h=12h+3h2h=12+3hm = \frac{(12 + 12h + 3h^2) - 12}{h} = \frac{12h + 3h^2}{h} = 12 + 3h

So, the slope of the secant line is 12+3h12 + 3h.

(C) The slope of the graph at (2,f(2))(2, f(2)):

The slope of the graph at a point is given by the derivative of the function. Let's compute the derivative of f(x)f(x):

f(x)=3x2f(x) = 3x^2 fβ€²(x)=ddx(3x2)=6xf'(x) = \frac{d}{dx}(3x^2) = 6x

Now, evaluate the derivative at x=2x = 2:

fβ€²(2)=6(2)=12f'(2) = 6(2) = 12

So, the slope of the graph at (2,f(2))(2, f(2)) is 12.


Would you like any further details or have any questions?

Here are 5 related questions to expand on this:

  1. What is the geometric interpretation of the slope of a secant line?
  2. How does the secant slope change as h→0h \to 0 in part (B)?
  3. How would you find the equation of the tangent line at x=2x = 2?
  4. What is the second derivative of f(x)=3x2f(x) = 3x^2, and what does it represent?
  5. Can you generalize the slope of the secant line for f(x)=axnf(x) = ax^n?

Tip: The derivative gives you the slope of the tangent line, which shows the rate of change of the function at any point.

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Math Problem Analysis

Mathematical Concepts

Algebra
Calculus
Derivatives
Secant Lines

Formulas

Slope of secant line: m = (f(x2) - f(x1)) / (x2 - x1)
Slope of secant line with h: m = (f(2 + h) - f(2)) / h
Derivative of a function: f'(x) = d/dx (f(x))

Theorems

Derivative definition
Slope of secant line as a limit of tangent

Suitable Grade Level

Grades 11-12 or Calculus I