Chapter 2: Problem 8
Given that \(f(-2)=3\) and \(f^{\prime}(-2)=-4,\) find an equation for the tangent line to the graph of \(y=f(x)\) at \(x=-2\)
Short Answer
Expert verified
The equation of the tangent line is \(y = -4x - 5\).
Step by step solution
01
Understand the Point-Slope Form
The equation of a line in point-slope form is given by \[ y - y_1 = m(x - x_1) \]where \((x_1, y_1)\) is a point on the line, and \(m\) is the slope of the line.
02
Identify the Point on the Graph
Since we know that when \(x = -2\), \(f(-2) = 3\), the point \((-2, 3)\) lies on the graph of the function \(y = f(x)\). This point will be \((x_1, y_1)\) in the point-slope form.
03
Identify the Slope of the Tangent Line
The derivative \(f'(x)\) at a point gives the slope of the tangent line at that point. We are given that \(f'(-2) = -4\), so the slope \(m\) of the tangent line is \(-4\).
04
Plug Values into Point-Slope Form
Substitute \((x_1, y_1) = (-2, 3)\) and \(m = -4\) into the point-slope form equation: \[ y - 3 = -4(x + 2) \]
05
Simplify the Equation
Distribute and simplify the equation to put it in slope-intercept form \(y = mx + b\):\[ y - 3 = -4x - 8 \]Add 3 to both sides:\[ y = -4x - 5 \]
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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 of a linear equation is a powerful tool in geometry and calculus. It's particularly useful for finding the equation of a line when you know one point on the line and the slope. The point-slope form is written as:\[ y - y_1 = m(x - x_1) \]Here, \((x_1, y_1)\) is your known point, and \(m\) is the slope of the line.
- The left side of the equation, \(y - y_1\), signifies the vertical distance from your point to any point \((x, y)\) on the line.
- The right side, \(m(x - x_1)\), represents the horizontal movement multiplied by the slope.
Derivative
In calculus, the derivative is a critical concept representing the rate of change or slope of a curve at any specific point. When you have a function like \(f(x)\), the derivative, denoted as \(f'(x)\), shows how \(f(x)\) changes as \(x\) changes.
- The derivative is fundamental in finding the tangent line, which touches the curve at precisely one point without crossing it.
- It tells us the slope at this very point, allowing us to draw a precise line that can model linear approximations of curves.
Slope-Intercept Form
The slope-intercept form of a linear equation is perhaps the most familiar form of a line equation to many students. It is expressed as:\[ y = mx + b \]This form directly reveals two critical pieces of information: the slope \(m\) and the y-intercept \(b\).
- The slope \(m\) informs you how steep the line is and in which direction it tilts.
- The y-intercept \(b\) provides the exact starting point where the line crosses the y-axis.