x + 3  y + z/(u + v)

FullForm[%]

%1^2

Expand[%]

Head[%]

Head[38]

Head[38. ]

Head[1.0 + 2.5  I]

Head[1 + 2  I]

Head[23/11]

Head[23/1]

Head[x]

Head[abc]

a = "Hiroshima"

Head[a]

a

a[x_] := x^2

?? a

Clear[a]

?? a

Head[a]

a = 38;
b = 23/11;
c = 1. ;

Head[c]

a*c

Head[%]

a + b

Head[%]

a + b + c

(2 + 3  I)^10

Exp[2 + 3  I]  // N

a = %36

Re[a]

Im[a]

Abs[a]

Arg[a]

(x + y I)^10

Expand[%]

Re[%]

ComplexExpand[Exp[x + I y]]

Expand[Exp[x +  I y]]

f = %43

Conjugate[f]

ComplexExpand[%]

(f + ComplexExpand[Conjugate[f]])/2

Expand[%]

?? a

Clear[a]

?? x

x = a

x

Clear[b, c]

y := b

y

3*(1 + 2

x = 3*(1 + 2

x

x := 3*(1 + 2

Random[]

x = Random[]

x

x

x := Random[]

x

x

a = 3

x = a

a = 6

x

x := a

x

a = 3

x

?? f

Clear[f]

f[x_] = x^2 + 1

x

f[x_] := x^2 + 1

f[5]

1 > 0

1 < 0

a = 38;
b = 11.

IntegerQ[a]

IntegerQ[b]

IntegerQ[a + b]

PrimeQ[a]

PrimeQ[b]

PrimeQ[2^100 + 1]

2 = >2

2 -> 2

2 ≥ 2

2 < 3  &&  3 < 1

2 < 3  ||  3 < 1

2 < 3  &&  3 < 4  &&  4 < 5

Clear[f]

f[x_] := If[x ≥ 0, 5  x, 2  x^2]

f[1]

f[-1]

Plot[f[x], {x, -2, 2}]

Clear[x]

Table[x^n, {n, 1, 10}]

Plot[{x, (x^2), (x^3), (x^4), (x^5), (x^6), (x^7), (x^8), (x^9), (x^10)}, {x, 0, 
        1}]

Plot[{x, (x^2), (x^3), (x^4), (x^5), (x^6), (x^7), (x^8), (x^9), (x^10)}, {x, 0, 
        1}, PlotRange -> {0, 1}]

Plot[Table[x^n, {n, 1, 10}], {x, 0, 1}, 
      PlotRange -> {0, 1}]

Plot[Evaluate[Table[x^n, {n, 1, 10}]], {x, 0, 1}, 
      PlotRange -> {0, 1}]

f[x_] := 
        If[x > 4, 2  x, 
          If[x^3 < -2, 1, x^3]];
Plot[f[x], {x, -2, 6}]