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May 25, 2015

Homework Help: Help with triangle

Posted by Garcelyn on Tuesday, August 29, 2006 at 5:53pm.

I need help with these:

Triangle LMN has vertices L(-6,5), M(-4,-3), N(-2,4). Find the coordinates of the vertices of its image after it is reflected over the x-axis and then translated by (-3,0)

a. L(-9,-5), M(-7,3), N(-5,-4)
b. L(-6,-5), M(-4,-3), N(-2,-4)
c. L(-5,-6), M(-7,3), N(-2,-4)
d. L(9,5), M(-4,-3), N(-5,-4)


The vertices of triangle FGH are F(1,1), G(3,-5), H(6,0). Find the coordinates of the vertices after a reflection over the y-axis.

a. J(0,0), K(1,-3), L(7,8)
b. J(0,0(, K(-1,3), L(-7,-8)
c. J(0,0), K(3,1), L(-8,-7)
d. J(0,0), K(-3,-1), L(8,-7)


For the first part, a reflection over the x-axis involves mutliplying the y coord's by -1. Thus
L(-6,5)-> (-6,-5), M(-4,-3)->(-4,3), N(-2,4)->(-2,-4). A translation involves adding (-3,0) to each of these points. Thus L(-6,-5)->(-6,-5)+(-3,0)=(-9,-5). You should be able to finish the others.

For the second one we reflect across the y-axis. This time we negate the x coord's. Thus F(1,1)->(-1,1).
It appears you're missing some kind of translation here. Was it supposed to be translated by (1,-1)? Or is it supposed to be reflected across the origin or some other point or line?


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