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प्रश्न
Examine, whether the following number are rational or irrational:
`(2-sqrt2)(2+sqrt2)`
उत्तर
Let `x=(2-sqrt2)(2+sqrt2)`
`rArrx=(2)^2-(sqrt2)^2` {As (a + b)(a - b) = a2 - b2}
⇒ x = 4 - 2
⇒ x = 2
So `(2-sqrt2)(2+sqrt2)` is a rational number
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