Margföldun – Æfing 3.4 – Lausnir

  1. (x + 3)2 = x2 + 2·3x + 9 = x2 + 6x + 9 (notum ferningsregluna)
  2. (2y + 4)2 = 4y2 +2·2y·4 + 16 = 4y2 + 16y + 16 (notum ferningsregluna)
  3. (z + 1)3 = (z2 + 2z + 1)(z + 1) = z3 + 2z2 + z + z2 + 2z + 1 = z3 + 3z2 + 3z + 1
  4. (p – 3q)2 = p2 – 2·3pq + 9q2 = p2 – 6pq + 9q2
  5. (2x – 3y)2 = 4x2 – 12xy + 9y2
  6. (3x + 1)2 = 9x2 + 6x + 1
  7. (5 – 2x)2 = 25 – 20x + 4x2
  8. (5x2 – 2x)2 = 25x4 – 2·5·2x3 + 4x2 = 25x4 – 20x3 + 4x2