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The simplest rationalising factor of 2sq...

The simplest rationalising factor of `2sqrt(5)-sqrt(3)` is
(a)`2sqrt(5)+ 3` (b) `2sqrt(5)+sqrt(3)` (c) `sqrt(5)+sqrt(3) ` (d) `sqrt(5)-sqrt(3)`

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Solution:
`(2sqrt(5)-sqrt(3)) xx (2sqrt(5)+sqrt(3))`
Using identity
`a^2-b^2 =(a+b)(a-b)`
`(2sqrt(5))^(2)- (sqrt(3))^(2)`
`= 20-3`
`=17`
Hence the correct option is `(a)`
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