(6/7)

f = x^2 + y^3

f

f^2

f =.

f

x = 2

f = x^2 + y^3

Clear[x];
f = x^2 + y^3

Clear[x];
f = x^2 + y^3

f = x^2 + y^3; 
    Print[f];  ;
g = x + y; Print[g]

Clear[f, g]

f

x^2 + y^3  /. x -> 2

ReplaceAll[x^2 + y^3, x -> 2]

x^2 + y^3  /.  {x -> 2, y -> 3}

Clear[f];
f[x_, y_] := x^2 + y^3

f[2, 3]

Clear[f];
f = x^2 + y^3

f^2

Expand[%]

Factor[%]

Factor[x^1000 - 1]

Factor[x^1000 - 1, Extension -> I]

Solve[x^3 + 4  x^2 - 2  x + 7 == 0, x]

Factor[1 + x + x^2,  GaussianIntegers -> True]

Collect[(1 + x y + 2  x^2 - y^2)^5, x, Factor]

?Collect

Series[
      80 (x^8) + 32 (x^10) + 80 (x^9) y - 
        10 (x^2) (((-1 + y))^3) (((1 + y))^3) + 
        5 x (((-1 + y))^4) y (((1 + y))^4) - (((-1 + y))^5) (((1 + y))^5) - 40 (x^7) y (-4 + 3 (y^2)) - 
        10 (x^3) (((-1 + y))^2) y (((1 + y))^2) (-4 + 
              3 (y^2)) - 10 (x^6) (-8 + 4 (y^2) + 3 (y^4)) + 
        5 (x^4) (-1 + y) (1 + y) (-8 + 4 (y^2) + 
              3 (y^4)) + (x^5) y (120 - 200 (y^2) + 81 (y^4)), {x, 0, 
        10}]

Factor[1 + x^3 + x^5 - x^6 + x^7]

Solve[1 - x + x^2 == 0, x]

Solve[1 - x^2 + x^3 == 0, x]

ReplaceAll[
      x^7  y^7 + x^5  y + x y^5 - 
        x y, {x -> (s + Sqrt[s^2 - 4  t])/2, 
        y -> (s - Sqrt[s^2 - 4  t])/2}]

Simplify[%]