y  =  (x^2 + 3  x + 2)/(x + 1)

Cancel[y]

y  =  (x - 1)/(x^2 + 3  x + 2)

Apart[y]

Together[%4]

Expand[%]

Expand[%]

ExpandAll[%]

FactorInteger[123456]

123456/(2^6*3)

Limit[ArcTan[x], x -> ∞]

Series[Sin[x], {x, 0, 7}]

D[x^2  u^2, x, u]

y =.

D[x^2 y^2, {x, 2}, {y, 2}]

Sin[2  x]  ==  Simplify[2*Cos[x]*Sin[x]]

FindRoot[Tan[x] == x, {x, 10}]

Solve[x^2 + a == 0, x]

Reduce[x^2 + a == 0, x]