((-1) ⋅ a) + a = 0

Start from the conclusion and work back up the proof. Click the arrow to show the parents.

• ((-1) ⋅ a) + a = 0,

  if the following are true:

  • a + b = c
  • a = d

  then d + b = c

  • (a ⋅ (-1)) + a = 0, (a ⋅ (-1)) + a = 0
  • a ⋅ (-1) = (-1) ⋅ a, a ⋅ b = b ⋅ a