\(y = \((x + 1)\)^5; 
Expand[y]\)

\(\(y = 1 + x; 
z = \((1 - x)\)*y; 
r = z^2; 

    f = \((r - y^2*z)\)/\((z - y^2)\); 
ExpandAll[f]
\)\)

Simplify[%]

\(x = 0.5; 
N[f]\)

\(Clear[x]; 
Clear[f]; 
f[x_] = Exp[\(-x^3\) + x^2 - x]; 

    s = Series[f[x], {x, 0, 5}]\)

N[Sum[1/n^2, {n, 1, 1000, 1}], 5]

(∑_(n = 1)^1000) (1/(n*n))  // N