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Ch. 3 - Derivatives
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243Not the one you use?Change textbook
Chapter 3, Problem 74a

Suppose f(3) = 1 and f′(3) = 4. Let g(x) = x2 + f(x) and h(x) = 3f(x).
Find an equation of the line tangent to y = g(x) at x = 3.

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Step 1: Identify the function g(x) and its components. We have g(x) = x^2 + f(x).
Step 2: To find the equation of the tangent line, we need the slope at x = 3. This requires finding g'(x), the derivative of g(x).
Step 3: Differentiate g(x) = x^2 + f(x) to get g'(x) = 2x + f'(x).
Step 4: Substitute x = 3 into g'(x) to find the slope of the tangent line: g'(3) = 2(3) + f'(3).
Step 5: Use the point-slope form of a line, y - y_1 = m(x - x_1), where m is the slope from Step 4, and (x_1, y_1) is the point (3, g(3)). Calculate g(3) using g(3) = 3^2 + f(3).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Tangent Line

A tangent line to a curve at a given point is a straight line that touches the curve at that point without crossing it. The slope of the tangent line is given by the derivative of the function at that point. For a function g(x), the equation of the tangent line at x = a can be expressed as y = g(a) + g'(a)(x - a).
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Slopes of Tangent Lines

Derivative

The derivative of a function measures how the function's output changes as its input changes. It is defined as the limit of the average rate of change of the function as the interval approaches zero. In this context, f'(3) = 4 indicates that at x = 3, the function f is increasing at a rate of 4 units of output for every 1 unit of input.
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Derivatives

Function Composition

Function composition involves combining two functions to create a new function. In this case, g(x) = x² + f(x) combines the polynomial function x² with the function f(x). Understanding how to differentiate composite functions is essential for finding the derivative g'(x), which is necessary for determining the slope of the tangent line.
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Related Practice
Textbook Question

{Use of Tech} The Witch of Agnesi The graph of y = a3 / (x2 + a2), where a is a constant, is called the witch of Agnesi (named after the 18th-century Italian mathematician Maria Agnesi).

Let a = 3 and find an equation of the line tangent to y = 27 / (x2 + 9) at x = 2.

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Textbook Question

Find an equation of the line tangent to the following curves at the given value of x.

y = 1+2 sin x; x = π/6

Textbook Question

Tangent lines Suppose f(2)=2 and f′(2) =3. Let g(x) = x²f(x) and h(x) = f(x) / x−3.

b. Find an equation of the line tangent to y = h(x) at x=2.

Textbook Question

The right-sided and left-sided derivatives of a function at a point aa are given by f+(a)=limh0+f(a+h)f(a)hf_{+}^{\(\prime\)}\(\left\)(a\(\right\))={\(\displaystyle\]\lim\)_{h\(\to\)0^{+}}{\(\frac{f(a+h)-f(a)}{h}\)}} and f(a)=limh0f(a+h)f(a)hf_{-}^{\(\prime\)}\(\left\)(a\(\right\))={\(\displaystyle\]\lim\)_{h\(\to\)0^{-}}{\(\frac{f(a+h)-f(a)}{h}\)}}, respectively, provided these limits exist. The derivative f(a)f^{\(\prime\)}\(\left\)(a\(\right\)) exists if and only if f+(a)=f(a)f_{+}^{\(\prime\)}\(\left\)(a\(\right\))=f_{-}^{\(\prime\)}\(\left\)(a\(\right\)).

Compute f+(a)f_{+}^{\(\prime\)}\(\left\)(a\(\right\)) and f(a)f_{-}^{\(\prime\)}\(\left\)(a\(\right\)) at the given point aa.

f(x)={4x2 if x12x+1 if x>1f(x)=\(\begin{cases}\)4-x^2~\(\text{if}\)~x\(\leq{1}\)\\2x+1~\(\text{if}\)~x\(\gt{1}\]\end{cases}\); a=1a=1

Textbook Question

Calculate the derivative of the following functions.

y = (p+3)² sin p²

Textbook Question

27–76. Calculate the derivative of the following functions.

y = √f(x), where f is differentiable and nonnegative at x.