Question

∆ABC is reflected about the line y = -x to give ∆A'B'C' with vertices
A'(-1, 1), B'(-2, -1), C(-1, 0). What are the vertices of ∆ABC?
A(1, -1), B(-1, -2), C(0, -1)
A(-1, 1), B(1, 2), C(0, 1)
A(-1, -1), B(-2, -1), C(-1, 0)
A(1, 1), B(2, -1), C(1, 0)
A(1, 2), B(-1, 1), C(0, 1)

Answer 1

Use the transformation for reflection about y=-x
s'(x,y): (x,y) -> (-y,-x)
and the inverse transformation is the identical (as is true with all reflections)
\((s')^{-1} : (x,y) -> (-y,-x)\)

For example, a point P(5,2) is reflected about y=-x, then P' is P'(-2,-5)
Calculate A, B, C point by point from the transformation of A', B', C' and you would find the answer in very little time.

Answer 2

i still am not understanding....what would the answer be ... @mathmate

Answer 3

i think it would be A(1, 2), B(-1, 1), C(0, 1) right

Answer 4

err no it would be A(-1, 1), B(1, 2), C(0, 1)....

Answer 5

Please read the example showing you how to do the transformation?
The transformation is
(x,y) ->(-y,-x)
so
(5,2)->(-2,-5)

Another example:
If P' is P'(4,-3), the P after transformation is P(3,-4).

Remember, in math, if you do not understand, ask how it works.
Guessing game is a game for life, you'll never get anywhere.

Answer 6

Yes, A(-1, 1), B(1, 2), C(0, 1). is correct. Well done!

Answer 7

thank you

Answer 8

You're welcome! :)