Which rule would result in a clockwise rotation of 90° about the origin? (x, y) → (x, -y)
(x, y) → (x + 4, y + 4)
(x, y) → (y, x)
(x, y) → (4x, 4y)

A : x, y -> x, -y

Could jaut look this up

in your graphing calculator you have to press the button (2nd) then (catalog) which is the number (0). 
after that you press (ALPHA) (L) which iOS the button for the parenthesis (. ).  )
find LOG and then plug in the number you want.
repeat this until you get the equation you want.