This video shows show to dilate a triangle on the coordinate plane by a scale factor of 1/2 and by a scale factor of 2/3. 

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This video shows how to reflect a triangle over the y-axis.  The triangle is located directly on top of the y-axis, so part of the triangle is on one side of the y-axis and part of the triangle is on the other side.
 

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This tutorial shows how you can reflect an object over a specified line segment.
 

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When reflecting objects across the x-axis, the x-values of each original point will remain the same and the y-values will become opposite.  This video shows how to apply this rule by reflecting an object over the x-axis.

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This tutorial shows how to reflect a triangle across the y-axis and identify the resulting points.

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