====== Expanding brackets ======

e.g. 

<math>3(x + 4y) = 3x + 12y</math>

Simplify the following expressions...

  - 2(x + y)
  - 3(x + 2y)
  - 2(2x + 2y)
  - 5(x - 2y)
  - -2(2x + y)
  - -3(x - 2y)
  - -3(-3x + 2)
  - 5(x - 2y) - 2x
  - 4(x - y) - 2(x + 2y)
  - 3(2x + y) + 2(x - 2y)
  - (x - y) - a(x + 2y)
  - 2x + 3y - (x - 3y)
  - 5(x - 2y - z) + 3(x - y + 2z)
  - 3(x + 8) - 4(2x - 5)
  - x(x + 1) 
  - x<sup>2</sup>(x - 7)
  - x<sup>3</sup>(x - 7) - x
  - x(x - 4) + 3(x - 2)
  - x(2x + 3) - 4(3x - 1)
  - x(x<sup>2</sup> + 1) - x<sup>2</sup>(x + 1)