Binomial expansion of modulus? How one can perform binomial expansion of modulus of a quantity. 
For example, can we expand |-1+x| ? If, yes how?
Thanks

Two cases it depends on (-1+x) value 
Case 1: (-1+x) is positive then write  it as $(x-1)^n$ and use normal binomial theorem 
Case 2: if (-1+x) is negative your answer is $-(x-1)^n$
Again if n is not a positive integer then you have to use 
$$(1+x)^n=1+nx+ \frac{n(n-1)}{1 \cdot 2} x^2 + \frac{n(n-1)(n-2)}{1\cdot2\cdot3} x^3+\cdots$$
So then case 1 will be $$(-1)^n \bigg[\frac{n(n-1)}{1 \cdot 2}x^2 + \frac{n(n-1)(n-2)}{1\cdot2\cdot3} x^3+ \cdots \bigg]$$
Case 2 will be $$(-1)^{n+1}\bigg[1+nx+ \frac{n(n-1)}{1 \cdot 2}x^2 + \frac{n(n-1)(n-2)}{1\cdot2\cdot3} x^3+ \cdots\bigg]$$
