If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

### Course: 6th grade (WNCP)>Unit 3

Lesson 6: Transformations

# Performing reflections

Sal shows how to perform a reflection on a quadrilateral using our interactive widget!

## Want to join the conversation?

• At , Sal moves the reflecting tool line to the line y=x+2. How does he know to move it at that point? How does he know where y=x+2 is?
• He knew that by using two pieces of information:
1- the slope of the line/reflecting tool which is the coefficient of variable x.
2- the y-intercept which is the intersection of the line/the tool with y-axis. The value of y-intercept is aways the constant in the right-hand side of the equation.
Hope this helps!
• Concept of reflection, that I can understand. Coefficient of x=1? Slope of 1? There you completely lost me. This reminds me of why I didn't understand math in high school 30 years ago. These sound like algebraic concepts, and I started with lower lessons because I wanted to work my way up to algebra, which is where my learning really went off the rails years ago. None of these "simple" explanations in the comments are doing it for me. A link to the lesson that explains these concepts, for reference, might help immensely. Otherwise, I'm almost at the end of the line with KA. Trying to explain a new concept with a concept that hasn't yet been taught makes exactly zero sense. In the form of an equation, makes sense=0. Please explain, or link to an explanation, that uses terms someone who hasn't learned algebra yet can understand. Thanks.
• I'm afraid that the Geometry course actually assumes you've already gone through both Algebra I and Pre-Algebra - if you click on 'subjects' over at the top left of your screen, you'll be able to see that they're formatted in that order. If you watch videos out of order, it's only to be expected that some concepts you haven't learned yet will show up.
However, some links you might find useful: the Algebra 1 course is at https://www.khanacademy.org/math/algebra, and the specific lessons that teach you about slope are here https://www.khanacademy.org/math/algebra/two-var-linear-equations#slope. ('Coefficient' is basic algebra vocabulary, and an explanation can be found in the very first algebra lessons.)
I hope this helped you; hopefully your experience with KA is improved by this tips. Wishing you good luck from a fellow KA student - although I'm still in school, instead of 30 years out :)
• I did not quite understand how SAL found the points 'y=x+2'... How do you do that?
• Consider the equation, y=x. The value of y is always the same as x. When x is 3, y is 3. When x is -105, y is -105. When x is the square root of pi, y is the square root of pi, etc. When graphed, a diagonal line is drawn through the origin (where x=0,y=0) and one end goes in the upright direction,
and the other end goes in the downleft direction. Saying that y=x+2 means that y is always 2 units more than x, therefore moving the line up 2 units. When in doubt, just plug in any number for x and use it to find y.
• but how do you do it without the tool, please make a video about that please like so it can go to the top and Khan can see this
• i dont understand how to do the y=x+2
• you plug in numbers for that equation.
if x=0, then y= 0+2, and therefore y=2 when x=0.
if x=1 then y=1+2, and therefore y=3 when x=1.
when x=2 then y=2+2 and then y=4.
plug it in, plug it in.
(1 vote)
• I can't manage a reflection after I establish the reflection line. Can't manage the widget! Any Ideas to help me?
• no, uhh, thee's this weird symbol line in the middle of the line, just click the half of it which isn't orange.
• I think that the more mistakes that you make, the more you learn; because you learn from your mistakes, and then build on them to answer correctly.
You know what you did wrong, and you won't repeat it. If you never made mistakes, you would never know how to react to them. You then learn from them great things that enable you to build around them, to a higher place that has never showed its face to you. As you soar to higher lands, you will make mistakes in the process. But, don't beat yourself up! For the very thing that you may feel bad about, may be the thing that led you to the higher place where you are today.🏆🥇📕
• so say the "y-intercept" is 2, you would find the number 2 on the y-axis and then from there you would go up one and over to the right one. until you have enough points then you start to go down one over one to complete your line. If the slope is -1 then you would start by going down 1 and then over to the left one.