Given that the triangle ABC is at A= (2,4) B= (5,9) C =(1,7) and if the triangle is reflected across the line y=1, what is the new position of point B?

We need not consider a whole triangle but just point B.

Before reflection we know that .

Reflecting B over is relatively easy. First because its a reflection over the horizontal line the only coordinates that will change are y coordinates, while x coordinate will not change so half of the reflection is already done for us,

Now to what has changed, well currently the distance between 9 and 1 on the y axis is 8 up. But because we are reflecting the a must now be 8 down from 1 which means so our point is now .

Hope this helps :)

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