These exercises are part of the lesson on conjugating the short form of verbs. 

Conjugate the following verbs to their short form

In the past positive

  1. おちる (to fall down)
  2. たす (to add)
  3. のる (to ride)
  4. あるく (to walk)
  5. なくす (to lose)

To the present negative

  1. かぜをひく (to catch a cold)
  2. わかれる (to break up)
  3. しんぱいする (to worry)
  4. よろこぶ (to be glad)
  5. できる (to be able)

To the past negative

  1. なおる (to be healed)
  2. こたえる (to answer)
  3. なる (to become)
  4. くる (to come)
  5. さく (to bloom)

You can find the answers behind this link