Analyze the Linear Function: y=-x+1 Properties and Solution

Linear Functions with Parallel Line Properties

Choose the correct answer for the function.

y=x+1 y=-x+1

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find the slope of the graph
00:04 Any number multiplied by 1 is always equal to itself
00:08 The coefficient of X is the slope of the graph
00:12 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

Choose the correct answer for the function.

y=x+1 y=-x+1

2

Step-by-step solution

Let's start with option A

In a linear function, to check if the functions are parallel, you must verify if their slope is the same.

y = ax+b

The slope is a

In the original formula:

 y = -x+1

The slope is 1

In option A there is no a at all, which means it equals 1, which means the slope is not the same and the option is incorrect.

 

Option B:

To check if the function passes through the points, we will try to place them in the function:

-1 = -(-2)+1

-1 = 2+1

-1 = 3

The points do not match, and therefore the function does not pass through this point.

 

Option C:

We rearrange the function, in a way that is more convenient:

y = -1-x

y = -x-1

You can see that the slope in the function is the same as we found for the original function (-1), so this is the solution!

 

Option D:

When the slope is negative, the function is decreasing, as the slope is -1, the function is negative and this answer is incorrect.

3

Final Answer

The graph is parallel to the graph of function

y=1x y=-1-x

Key Points to Remember

Essential concepts to master this topic
  • Slope Rule: Parallel lines have identical slopes for linear functions
  • Technique: Compare y=x+1 y = -x + 1 with y=x1 y = -x - 1 slopes
  • Check: Substitute point coordinates: 1=(2)+1=3 -1 = -(-2) + 1 = 3 fails ✓

Common Mistakes

Avoid these frequent errors
  • Confusing slope identification in different forms
    Don't assume y = -1 - x has slope -1! This equals y = -x - 1 where slope is -1, not +1. Students mix up the coefficient of x when terms are rearranged. Always rewrite in standard y = mx + b form first.

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

How do I find the slope when the equation looks different?

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Always rewrite in standard form y=mx+b y = mx + b first! For example, y=1x y = -1 - x becomes y=x1 y = -x - 1 , so the slope is -1.

Why aren't y = -x + 1 and y = x + 1 parallel?

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Their slopes are different! The first has slope -1, the second has slope +1. Parallel lines must have exactly the same slope but different y-intercepts.

How do I check if a point lies on the line?

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Substitute the x-coordinate into the equation and see if you get the y-coordinate. For (2,1) (-2, -1) : 1=?(2)+1=3 -1 \stackrel{?}{=} -(-2) + 1 = 3 False!

What makes a function increasing or decreasing?

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Look at the slope! Positive slope = increasing function, negative slope = decreasing function. Since y=x+1 y = -x + 1 has slope -1, it's decreasing.

Can two different equations represent parallel lines?

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Yes! y=x+1 y = -x + 1 and y=1x y = -1 - x are parallel because they both have slope -1, just different y-intercepts (1 and -1).

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