Triangle pqr is transformed to triangle p'q'r'. triangle pqr has vertices p(3, −6), q(0, 9), and r(−3, 0). triangle p'q'r' has vertices p'(1, −2), q'(0, 3), and r'(−1, 0). plot triangles pqr and p'q'r' on your own coordinate grid. part a: what is the scale factor of the dilation that transforms triangle pqr to triangle p'q'r'? explain your answer. (4 points) part b: write the coordinates of triangle p"q"r" obtained after p'q'r' is reflected about the y-axis. (4 points) part c: are the two triangles pqr and p''q''r'' congruent? explain your answer. (2 points

(A)
The transformation from PQR to P'Q'R' is a dilation, with the scale factor equal to P'Q'/PQ=Q'R'/QR=R'P'/RP=1/3
Scale factor is the ratio of the image (dilated) linear dimension divided by the preimage (original) linear dimension.

(B)
When reflected about the y-axis, the sign of the x-coordinates are reversed.  All other values remain unchanged, i.e. (x,y)->(-x,y)
Therefore
P'(1, −2)  -> P"(-1,-2)
Q'(0, 3) -> Q"(0,3)
R'(−1, 0) -> R"(1,0)

(C)
PQR and P"Q"R" are not congruent, since P"Q"R" has undergone two transformations. 
The first transformation is a dilation with a scale factor of 1/3, which does not preserve dimensions, but preserves angles.  
The second transformation is a reflection, which preserves both dimensions and angles.
Therefore, P'Q'R' is congruent to P"Q"R".
PQR is NOT congruent to P"Q"R", but is similar to it (preservation of angles).