(x-y)^4 + (x+y)^4

Expand[%]

Factor[%]

D[ x^2 Cos[x^2] Sin[x^2] , x ]

Factor[Simplify[%]]

Series[Tan[x]/x,{x,0,10}]

Series[ (f[x+h]+f[x-h]-2f[x])/h^2, {h,0,4}]

a x^2 + b x + c ==0

Solve[%,x]

Solve[ {a x + b y == p, c x + d y == q}, {x,y}]

Simplify[%]

NSolve[ z^4 + 2 == 0, z ]

FindRoot[ {Sin[x] - y^2 ==0, Cos[y] - x^2 ==0},
          {x,1}, {y,1} ]

DSolve[ y''[x] + k y[x] == f, y[x], x ]

NDSolve[ {y''[x] + Sin[y[x]] == Cos[x] ,
          y[0] == 1, y'[0] == 0 }, y, {x,0,50} ]

Plot[ Evaluate[ y[x] /. % ], {x,0,50} ];