sqrt(15)=3.88" eass "sqrt((5)/(3))=?

Given x, y in R , x^(2) + y^(2) gt 0 . Then the range of (x^(2) + y^(2))/(x^(2) + xy + 4y^(2)) is (a) ((10 - 4 sqrt(5))/(3),(10 + 4 sqrt(5))/(3)) (b) ((10 - 4 sqrt(5))/(15),(10 + 4 sqrt(5))/(15)) (c) ((5- 4 sqrt(5))/(15),(5 + 4 sqrt(5))/(15)) (d) ((20- 4 sqrt(5))/(15),(20 + 4 sqrt(5))/(15))

Divide 15sqrt(15) by 3sqrt(5)

If sqrt(15)=3.88, find the value of sqrt((5)/(3))

If both a and b are rational numbers,find the values of a and b in each of the following equalities :(sqrt(3)-1)/(sqrt(3)+1)=a+b sqrt(3)( ii) (3+sqrt(7))/(3-sqrt(7))=a+b sqrt(7)(5+2sqrt(3))/(7+4sqrt(3))=a+b sqrt(3)( iv) (5+sqrt(3))/(7-sqrt(3))=47a+sqrt(3)b(sqrt(5)+sqrt(3))/(sqrt(5)-sqrt(3))=a+b sqrt(15) (iv) (sqrt(2)+sqrt(3))/(3sqrt(2)-2sqrt(3))=1-b sqrt(3)

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

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)