1. Find the volume of a cube whose surface area is 24 units?

2. If r and s are roots of the equation x^2 – x – 1 = 0 then find the value of 1/r2 + 1/s2 ?

1. Answer:8 cubic units

Solution:If ‘a’ is side of a cube, then the surface area = 6a^2 = 24 and so a = 2. Hence the volume = a^3 = 2^3 = 8.

2. Answer:3

Solution:1/r2 + 1/s2 = (r2 + s2)/(rs)2 = [(r + s)2 – 2rs]/(rs)2 = [1 – 2(-1)]/(-1)2 = 3.

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