Question

[Nguyễn Thanh Trúc]

Chứng minh   \(\dfrac{1}{a.\left(a+1\right)}\) = \(\dfrac{1}{a}\)+ \(\dfrac{-1}{a+1}\)

Answer 1

[Duan Ta]

quy đồng 1/a + (-1/(a+1) = 1/a(a+1) + (-a/a(a+1) = (a+1-a)/a(a+1) = 1/a(a+1)

Answer 2

[Kiều Vũ Linh]

Ta có:

VP = 1/a + [-1/(a + 1)]

= (a + 1 - a)/[a.(a + 1)]

= 1/[a(a + 1)]

= VT

Vậy 1/[a.(a + 1)] = 1/a + [-1/(a + 1)]