If 1/{a+b}=1/a+1/b , then the value of a^3-b^3 is

SSC CHSL 20 Dec 2015 Shift 2 Paper

Question : 148 of 200

Marks: +1, -0

1/{a+b}=1/a+1/b

, then the value of

a^3-b^3

Solution:

Given :

1/{a+b}=1/a+1/b

⇒

1/{a+b}={a+b}/{ab}

⇒

(a + b)^2 = ab

⇒

(a ^2 + b ^2+ 2ab) − ab = 0

⇒

a^2+b^2+ab=0

---(i)
To find :

a^3-b^3

(a − b)(a ^2 + b^ 2 + ab)

Using equation (i), we get :
⇒

(a − b) × 0 = 0

Go to Question:

Prev Question

Next Question