Chapter 2: Problem 7
Given that \(f(3)=-1\) and \(f^{\prime}(3)=5\), find an equation for the tangent line to the graph of \(y=f(x)\) at \(x=3\).
Short Answer
Expert verified
The equation of the tangent line is \(y = 5x - 16\).
Step by step solution
01
Understand the Problem
To find the equation of the tangent line to the curve \(y=f(x)\) at a specific point \(x=3\), we need a point on the line and the slope of the line at that point.
02
Identify Known Values
From the problem, we know two critical values: \(f(3) = -1\), meaning the point where the tangent line touches the curve is \((3, -1)\), and \(f'(3) = 5\), which is the slope of the tangent line at \(x=3\).
03
Use Point-Slope Formula
The point-slope form of a line is given by the formula \(y - y_1 = m(x - x_1)\), where \((x_1,y_1)\) is a point on the line, and \(m\) is the slope. Here, \(x_1 = 3\), \(y_1 = -1\), and \(m = 5\).
04
Substitute Values into the Equation
Substitute the known values into the point-slope equation: \(y - (-1) = 5(x - 3)\). Simplify it to get the equation: \(y + 1 = 5(x - 3)\).
05
Simplify the Equation
Reorganize the equation into slope-intercept form (\(y = mx + b\)) or another preferred form: Solve \(y + 1 = 5(x - 3)\) to get \(y = 5x - 15 - 1\), which simplifies to \(y = 5x - 16\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Point-Slope Form
The point-slope form is a very handy way to write the equation of a line. It's particularly useful when you know a single point on the line and the slope of the line. This form is expressed as:
Using this form is like building the bridge between a point and the slope, which gives you a clear path to finding the equation of the line. This approach is straightforward for writing down tangent lines, as it directly relates to the change in your function at a specific point.
- \[ y - y_1 = m(x - x_1) \]
- In this formula, \((x_1, y_1)\) is the point with coordinates on the line.
- \(m\) represents the slope, which shows how steep the line is.
Using this form is like building the bridge between a point and the slope, which gives you a clear path to finding the equation of the line. This approach is straightforward for writing down tangent lines, as it directly relates to the change in your function at a specific point.
Derivative
Derivatives are a core concept in calculus and serve as a measure of how a function is changing at any given point. Essentially, the derivative provides us with the function's slope at any location.
When finding a tangent line to a curve, the derivative is crucial. This is because the derivative at a specific point gives the exact slope of the tangent line there. In our context, with \(f'(3) = 5\):
When finding a tangent line to a curve, the derivative is crucial. This is because the derivative at a specific point gives the exact slope of the tangent line there. In our context, with \(f'(3) = 5\):
- The value \(5\) is the slope of the tangent line at \(x=3\).
- This reflects how the function \(f(x)\) behaves at that precise location.
Slope-Intercept Form
The slope-intercept form is another popular way to express the equation of a line. It is expressed as:
In our case, after simplifying from the point-slope form, we found:
- \[ y = mx + b \]
- Here, \(m\) stands for the slope, giving the steepness of the line.
- \(b\) is the y-intercept, which is the point where the line crosses the y-axis.
In our case, after simplifying from the point-slope form, we found:
- \[ y = 5x - 16 \]
- Here, the slope \(m\) is \(5\), indicating the line is going upwards fairly quickly.
- The y-intercept \(b\) is \(-16\), showing where the line crosses the y-axis.