Question

check whether (2√5+√7)(2√5-√7) is rational or irrational

Answer 1

thanks. given us
(2√5+√7) (2√5-√7)
= (2√5)² - (√7)²
= 4×5 - 7
= 20 - 7
= 13
we know 13 is a rational number that's why (2√5+√7) (2√5-√7) is a rational
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