RRB Non Technical Model Papers 8 with solutions

Question : 56 of 100

Marks: +1, -0

If x + y = 4 and

1/x+ 1/y = 4,

then the value of

x^3 + y^3

is:

Solution:

⇒x y ={x+y}/xy= 4

⇒xy={x+y}/4 =4/4 = 1∵ (x + y)^3 =

x^3 + y^3 + 3xy (x + y) ⇒ 4^3 = x^3 + y^3 +3 × 1× 4 ∴ x^3 + y^3 = 64 - 12 = 52

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