Why do these geometrical transformations have different answers?

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Ok so there's 2 questions asking to describe the geometrical transformations from

y=2^x onto y=2^(x+7) +3   (answer: translation by vector (-7, 3) )

y=2^4x onto y=2^(4x-3)     (answer: stretch in y direction, scale factor 1/8)

i understand where both answer are coming from but i don't understand why in the first one when the a number is added to the power it is a translation but then in the 2nd a number is took away from the power, this is a stretch? i would of thought they would both be translations or stretches

in an exam how could i tell if it was a strech or a translation? 


Posted Mon 14th May, 2012 @ 18:52 by Emily

1 Answer

  • 0 votes

if it is was translation it is done to the X ONLY.

so if the second one was to be a translation vector (3,0) it would go to y=2^(4(x-3))

if you don't understand please do just ask, I'm happy to help.


is the first one meant to read y=2^((x+7) +3)    or y=2^ (x+7)  + 3 (where the 3 is not in the power)

if the first one, then the first one is a translation of vector (-10, 0)

hope this helps:)


Answered Mon 14th May, 2012 @ 19:58 by Pui Pui