A function f(x) is linear and has a value of 29 at x = – 2 and 39 at x = 3. Find its value at x = 5.
43
A linear function is a function whose graph is a straight line. It can be represented by the equation \(f(x) = mx + c\), where \(m\) is the slope of the line and \(c\) is the y-intercept. In this problem, we are given two specific values of the function at two different x-values and asked to find the value of the function at another x-value.
The first step to finding the equation of the linear function is to determine its slope (\(m\)). The slope is calculated using the formula:
$$m = \frac{y_2 - y_1}{x_2 - x_1}$$
We are given two points on the line:
Now, let's substitute these values into the slope formula:
$$m = \frac{39 - 29}{3 - (-2)}$$ $$m = \frac{10}{3 + 2}$$ $$m = \frac{10}{5}$$ $$m = 2$$
So, the slope of the linear function is \(2\).
Now that we have the slope (\(m = 2\)), we can use one of the given points to find the y-intercept (\(c\)) of the linear function. We will use the general form \(f(x) = mx + c\). Let's use the point \((x, f(x)) = (-2, 29)\):
$$f(x) = mx + c$$ $$29 = (2)(-2) + c$$ $$29 = -4 + c$$
To find \(c\), we add \(4\) to both sides of the equation:
$$c = 29 + 4$$ $$c = 33$$
Thus, the equation of the linear function is:
$$f(x) = 2x + 33$$
The final step is to find the value of the linear function at \(x = 5\). We will substitute \(x = 5\) into the equation \(f(x) = 2x + 33\):
$$f(5) = 2(5) + 33$$ $$f(5) = 10 + 33$$ $$f(5) = 43$$
Therefore, the value of the linear function at \(x = 5\) is \(43\).
Here is a quick summary of how we found the value of the linear function:
| Step | Description | Calculation/Result |
|---|---|---|
| 1. Calculate Slope | Using two given points, \((-2, 29)\) and \((3, 39)\). | \(m = \frac{39 - 29}{3 - (-2)} = \frac{10}{5} = 2\) |
| 2. Find Y-intercept | Using slope \(m=2\) and point \((-2, 29)\) in \(f(x) = mx + c\). | \(29 = 2(-2) + c \implies c = 33\) |
| 3. Form Equation | Write the full equation of the linear function. | \(f(x) = 2x + 33\) |
| 4. Evaluate at x=5 | Substitute \(x=5\) into the function's equation. | \(f(5) = 2(5) + 33 = 10 + 33 = 43\) |
The final value of the linear function at \(x = 5\) is \(43\).
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