A bit of confusion I am having with compression and expansion.

1.

Original was a -5.

Compress horizontally by a factor of 1/5. New equation: y=f(5x)

2.

Expand horizontally by a factor of 3. New equation: y=f(1/3x)

3.

Compress horizontally by a factor of 1/4. New equation: y=(4x)

4.

Compress horizontally by a factor of 2/9. New equation: y=(-9/2x)

Basically what I am asking is shouldn't number 3beEXPANDbecause it is a positive? It might be an error on my sheet but it is printed from my teacher, so I am right now.

Oh and shouldn't number 1's new equation be: y=f(-5x)?

It would make sense if expand for positive and compress for negative.. unless this idea is wrong..