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## High school geometry

### Course: High school geometry > Unit 1

Lesson 3: Translations# Determining translations

Learn how to find the necessary translation to map a given source shape onto a given image shape.

In this article, we will solve problems where we are given starting and ending coordinates and asked to figure out what translation must have occurred.

## Part 1: Determining the translation for a single pair of points

### Let's study an example problem

A translation maps point $A(3,7)$ to point ${A}^{\prime}(6,-2)$ . Let's determine what translation this is.

#### Solution

**Step 1: Horizontal shift.**

**Step 2: Vertical shift.**

**The answer:**$A$ is mapped onto ${A}^{\prime}$ under a translation by $\u27e8{3},{-9}\u27e9$ .

### Your turn!

#### Problem 1

#### Problem 2

#### Problem 3

#### Challenge problem

A certain translation takes point $D(-3,10)$ to point ${D}^{\prime}(-12,21)$ .

## Part 2: Determining the translation for a pair of polygons

### Let's study an example problem

Consider the quadrilaterals drawn below. Let's determine the translation that maps the pre-image ${FGHI}$ onto the image ${{F}^{\prime}{G}^{\prime}{H}^{\prime}{I}^{\prime}}$ .

#### Solution

Let's focus in on a pair of corresponding points, such as $F(-4,6)$ and ${F}^{\prime}(2,3)$ . If we can find the translation that takes $F$ to ${F}^{\prime}$ , we will necessarily know the translation that takes the entire pre-image quadrilateral to its image!

**Horizontal shift:**

**Vertical shift:**

**Therefore,**$FGHI$ is mapped onto ${F}^{\prime}{G}^{\prime}{H}^{\prime}{I}^{\prime}$ under a translation by $\u27e8{6},{-3}\u27e9$ .

### Your turn!

## Want to join the conversation?

- I don't get this problem:

Challenge problem

A certain translation takes point D (-3, 10) to point D'(-12, 21).

What is the image of E(17, -9) under this translation?

I tried (-9, 11), since you need -9 to from -3 to -12, and 11 since it's 11 from 10 to 21; I also tried (9, -11). Can someone please explain what i'm doing wrong? Thanks!(37 votes)- You must get the translation by taking the difference between D'(-12,21) and D(-3,-10).Then you will get (-9,11).You must apply this to E(17,-9).So you will get the answer(14 votes)

- The challenge problem is not making any sense, even after watching the video they give you for help. Is there an easier way to understand this or an easier way for it to be explained?(36 votes)
- You have to take the translation from the first problem and add it to the third coordinate. So if it was point A at (7,12) to point B at (11,4). The translation is (4,-8). Now you apply that to point C at (10,15), 10+4, 15-8. So your final point is at (14,7).(5 votes)

- If i choose to type only what i got for a certain point, will it be the same as the other points or will I get it wrong? This confuses me.(15 votes)
- It will be the same as all the points moved the same amount. If that makes sense. I just realized this was 5 years ago, oops!(6 votes)

- To get the translation vector i can use any points ... for example a object point - any image point = Translation Vector... Well nothing seems to change i get the same result with every point.. So i dont have to do it for every point right? Can i just use one and thats it ?(17 votes)
- Yes you can use any point. It is best to use a vertex though. Yes you only need to use one point( see https://www.khanacademy.org/math/math1/x89d82521517266d4:transformations/x89d82521517266d4:translations/v/formal-translation-tool-example)(0 votes)

- I don't get this(5 votes)
- You translate it think jared think(31 votes)

- Choosing J, the initial point is at (2,-4). That point then moves to J' at (-2,3)

-2-2=-2+(-2)=-4

3-(-4)=3+4=7

This would make the translation (-4,7). Please help. This is EXTREMELY frustrating and I can't move ahead until I understand where my mistake is(14 votes)- your correct you didn't make a mistake(4 votes)

- I forgot a negative XD(14 votes)
- I dont get how to do this it is very confusing to me(10 votes)
- Where are you getting confused? You are trying to find the vertex from a preimage point (no tic mark) to an image point (with a prime), so you subtract the <x'-x,y'-y> to get a vector, and once you find the vector, all points of a figure will be translated along the same vector. Take the last example using J. J is at (2,-4) and J' is at (-2,3). The translation it moved along would be (-2-2,3-(-4)) or (-4,7). Always make sure you know the preimage and the image that you are translating to.(5 votes)

- I'm confused o n this and the whole next segment I've been over the materal and still can not figure out what to do , do you have any tips to help me?(11 votes)
- for the your turn problem of translating a shape, i got point k on jkl as 8, -3, and k' of triangle j'k'l' as 4,4. the translation i got was 4, -7. it is coming up as incorrect and i dont know what im doing wrong. could you please tell me what i did? thank you for your time and have a great day!(5 votes)
- You are describing the translation that maps
**J'K'L' onto JKL**.(10 votes)