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Question

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.

The correct answer is

43

Linear Function Problem Overview

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.

Calculating the Slope of the Linear Function

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:

  • Point 1: \(x_1 = -2\), \(f(x_1) = y_1 = 29\)
  • Point 2: \(x_2 = 3\), \(f(x_2) = y_2 = 39\)

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 \(2\).

Determining the Equation of the Linear Function

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:

$$f(x) = 2x + 33$$

Finding the Function Value at x = 5

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 \(43\).

Summary of Steps for Linear Function Value

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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Important Questions from Numerical Computation

  1. Ratio of the angles of a triangle are 1 : 2 : 6. What is the smallest angle?

  2. It would take one machine 4 hours to complete a production order and another machine 2 hour to complete the same order. If both machines work simultaneously at their respective constant rates, the time taken to complete the same order is ________ hours.

  3. Two design consultants, P and Q, started working from 8 AM for a client. The client budgeted a total of USD 3000 for the consultants. P stopped working when the hour hand moved by 210 degrees on the clock. Q stopped working when the hour hand moved by 240 degrees. P took two tea breaks of 15 minutes each during her shift, but took no lunch break. Q took only one lunch break for 20 minutes, but no tea breaks. The market rate for consultants is USD 200 per hour and breaks are not paid. After paying the consultants, the client shall have USD_remaining in the budget.

  4. What is the value of \(1 + \frac{1}{4} + \frac{1}{{16}} + \frac{1}{{64}} + \frac{1}{{256}} + \ldots ?\)

  5. A 1.5 m tall person is standing at a distance of 3 m from a lamp post. The light from the lamp at the top of the post casts her shadow. The length of the shadow is twice her height. What is the height of the lamp post in meters?

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