For the Transformation T, write the T^-1.T : (x, y) (5x, 5y )T^ -1 (x, y) (x - 5, y - 5)(5x - 1, 5y - 1)(1/5x, 1/5y)

The 3rd selection is appropriate.

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(1/5)(5x) = x, so the inverse transformation returns the original. Not so for the other choices.