Linear Function: Match the Equation to Table Values (-2,4), (-1,2), (1,-2)

Linear Functions with Table Point Verification

Below is a table containing values for x and y. This tables represents a linear function.

Choose the equation that corresponds to the function.

-2-11x42-2y

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find the algebraic representation for the given table
00:04 Let's take 2 given points
00:12 Use the formula to find the slope using 2 points on the graph
00:16 Substitute appropriate values according to the data, and solve to find the slope
00:29 This is the graph's slope
00:39 Use the formula for linear function representation
00:43 Substitute the points and solve to find the unknown B
00:52 Isolate B
00:57 This is the intersection point with the Y-axis (the unknown B)
01:03 Substitute accordingly the slope and intersection point to find the function
01:10 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Below is a table containing values for x and y. This tables represents a linear function.

Choose the equation that corresponds to the function.

-2-11x42-2y

2

Step-by-step solution

To find the equation of the linear function corresponding to the given table, follow these steps:

  • Step 1: Identify Points
    We have three points from the table: (2,4)(-2, 4), (1,2)(-1, 2), and (1,2)(1, -2).
  • Step 2: Calculate the Slope
    The slope mm can be calculated using any two points. Choosing (2,4)(-2, 4) and (1,2)(-1, 2):
    m=y2y1x2x1=241(2)=21=2 m = \frac{y_2 - y_1}{x_2 - x_1} = \frac{2 - 4}{-1 - (-2)} = \frac{-2}{1} = -2 .
  • Step 3: Verify Linear Relationship
    Using (x,y)(x, y) pairs, check another pair such as (1,2)(-1, 2) and (1,2)(1, -2):
    m=221(1)=42=2 m = \frac{-2 - 2}{1 - (-1)} = \frac{-4}{2} = -2 .
  • Step 4: Select the Correct Equation
    The slope is 2-2, and since a linear function typically can be formatted as y=mx+by = mx + b, we can see if b=0b = 0 by trying one of the equations y=2xy = -2x given in the choices. Let’s check:
    For x=2x = -2: y=2(2)=4y = -2(-2) = 4. Matches.
    For x=1x = -1: y=2(1)=2y = -2(-1) = 2. Matches.
    For x=1x = 1: y=2(1)=2y = -2(1) = -2. Matches.
  • Therefore, the equation that corresponds to the function is y=2x y = -2x .

3

Final Answer

y=2x y=-2x

Key Points to Remember

Essential concepts to master this topic
  • Slope Formula: Use any two points to calculate slope m = (y₂ - y₁)/(x₂ - x₁)
  • Technique: Calculate slope: m = (2 - 4)/(-1 - (-2)) = -2/1 = -2
  • Check: Verify equation y = -2x works for all points: (-2,4), (-1,2), (1,-2) ✓

Common Mistakes

Avoid these frequent errors
  • Using wrong points or calculating slope incorrectly
    Don't mix up coordinates or subtract in wrong order = wrong slope! If you calculate (4 - 2)/(-2 - (-1)) = 2/(-1) = -2, you get the right slope by accident but used wrong method. Always use (y₂ - y₁)/(x₂ - x₁) in correct order.

Practice Quiz

Test your knowledge with interactive questions

For the function in front of you, the slope is?

XY

FAQ

Everything you need to know about this question

Why do I need to check multiple points when finding the slope?

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Verification is key! Calculate the slope using two different pairs of points. If you get the same slope both times, you know the function is truly linear and your calculation is correct.

How do I know which equation to choose from the options?

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First find the slope from the table points. Then test each answer choice by substituting one point into each equation. The correct equation will make the point true!

What if the y-intercept isn't zero like in y = -2x?

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Many linear functions have the form y=mx+b y = mx + b where b ≠ 0. Check if any point has x = 0 in your table, or use point-slope form to find b.

Can I use any two points to find the slope?

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Yes! For a true linear function, any two points will give you the same slope. If you get different slopes, the function isn't linear or you made a calculation error.

How do I verify my final answer is correct?

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Substitute all given points into your chosen equation. For y=2x y = -2x : (-2,4) gives 4 = -2(-2) = 4 ✓, (-1,2) gives 2 = -2(-1) = 2 ✓, (1,-2) gives -2 = -2(1) = -2 ✓

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