(1+x)^-2 = ?Explain it.------------------------------

binomial expansion of(1+x)^n , where n is a negative power,

(1+x)^-2 = 1+nx +n(n-1)x^2/2! +n(n-1)(n-2)x^3/3! +… an infinite series true for |x| less than 1.

=1+(-2)x +(-2)(-3)x^2/2! +(-2)(-3)(-4)x^3/3! +…

=1–2x +3x^2 -4x^3 +…