$1-\frac{1}{2}x$

$1-x+\frac{1}{2}{x}^2$

$1-x+x^2-\frac{1}{2}{x}^3$

$1-x+x^2-x^3+\frac{1}{2}{x}^4$

$1-\frac{3}{4}x+\frac{1}{4}{x}^2$ $1-x+\frac{3}{4}{x}^2-\frac{1}{4}{x}^3$ $1-x+x^2-\frac{3}{4}{x}^3+\frac{1}{4}{x}^4$

$1-\frac{7}{8}x+\frac{4}{8}{x}^2-\frac{1}{8}{x}^3$ $1-x+\frac{7}{8}{x}^2-\frac{4}{8}{x}^3+\frac{1}{8}{x}^4$

$1-\frac{15}{16}x+\frac{11}{16}{x}^2-\frac{5}{16}{x}^3+\frac{1}{16}{x}^4$