Q. 83.7( 3 Votes )
Which of th A. (ii), (iii) and (iv)
B. (i), (ii) and (iv)
C. (i), (ii) and (iii)
D. (i), (iii) and (iv)
Answer :
i.√(2 + √3 ) is irrational ∵ √3 is irrational and 2 is rational and sum of a rational and irrational number is always irrational. Hence 2 + √3 is irrational. Hence, its square root is also irrational.
ii.√(4 + √25) is rational ∵ √25( = 5) is rational and 4 is also rational.
Hence, √(4 + 5) = √9 = 3 is rational.
iii. ∛(5 + √7) is irrational ∵ √7 is irrational and 5 is rational and sum of a rational and irrational number is always irrational. Hence 5 + √7 is irrational. Hence, its cube root is also irrational.
iv.√(8-∛8 ) is irrational. Here both ( = 2) and 8 are rational. Hence
8 – 81/3 = 8 – 2 = 6 is rational. But √6 is irrational.
Hence, the answer.
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