Question

What is the reflection image of P(0, 0) after two reflections, first across x = -3 and then across y = 4?
A. (4, -3)
B. (-6, 8)
C. (4, -6)
D. (-8, -6)

Answer 1

Ok, so lets start by shifting the point P about x=-3 line. Its distance from x=-3 is 3 units to the right. So when I reflect it about x=-3, its new distance will still be 3 units, but in the opposite direction of the x=-3 line. So whats the new x co-ordinate of P?

Answer 2

im still kind of confused. would it be (0, -3)?

Answer 3

Ok first of all, only the x co-ordinate would change, not the Y. So your answer is wrong. Secondly, look at it this way: Think of the x =-3 line as a mirror. Now a point on the right side of this mirror....where does it appear on the left side of the mirror? Remember, the distance will be same, only the direction will change.

Answer 4

so it would be (-3,0)?

Answer 5

Correct! So you have the answer for the first reflection. Similarly, now consider the y=4 line as the mirror. Now where would the point appear? This time, its X co-ordinate remains the same, only the Y changes. Remember: same distance!!

Answer 6

okokok

Answer 7

Actually, you don't even need to bother with finding that out. The only option with -6 as the x co-ordinate is A, so thats the answer.

Answer 8

oh ok. thank you :)

Answer 9

Welcome!!! What course is this btw?

Answer 10

geometry

Answer 11

LOL that I am aware of. I am asking which grade?

Answer 12

HAHAHAHA oh it was supposed to be a sophomore class. but i never took it.

Answer 13

Cool...no problems, you are getting the hang of it. You should be able to ace this soon!

Answer 14

awe, thank you :)