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sanaa.rizwan
- Senior | Next Rank: 100 Posts
- Posts: 69
- Joined: Wed Aug 08, 2012 9:00 am•Followed by: 1 member
√80 can be written as 4√5. So 3√80 = 3*4√5 or 12√5
Multiply right side of the expression (both numerator and denominator) by (9-4√5) that will give:
=> [3 * (9-4√5)] / [(9+4√5) * (9-4√5)]
=>(27 - 12√5) / (81-80)
=> (27- 12√5)
Adding left side of the expression to the right side we get: root(12√5 + 27- 12√5)
=√27 = 3√3
Ans C
