$1 + \frac{1}{2}(x-1) - \frac{1}{8}(x-1)^2$

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

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

$1 - (x-1) + (x-1)^2$