SSC CGL 9 Aug 2015 Shift 2 Paper

Question : 137 of 200

Marks: +1, -0

If m – 5n = 2, then the vlaue of (

m^3 – 125n^3

– 30 mn) is

Solution:

m – 5n = 2
On cubing both sides,

(m – 5n)^3

2^3

⇒

m^3 – (5n)^3

– 3 × m × 5n (m – 5n) = 8
⇒

m^3 – 125n^3

– 15mn × 2 = 8
⇒

m^3 – 125n^3

– 30mn = 8

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