Could someone explain me question 9 you

R1 / r2 = sqrt(m2)  / sqrt(m1)  Notice the numbering system. If the 2 is on the denominator for the r, then it will be in the numerator for the m. You must substitute carefully.

r1 / r2 = sqrt(30) / sqrt(12) 
r1 / r2 = sqrt(2)*sqrt(3)(sqrt(5) / sqrt(3) sqrt(4) but sqrt(4) = 2.

ri / r2 = sqrt(2)* sqrt(3)*sqrt(5) / sqrt(3) * 2 Now you can cancel out sqrt(3)
r1 / r2 = sqrt(2)*sqrt(5) / 2

r1 / r2 = sqrt(10)/2 <<<< answer
B <<< answer. Notice that they put sqrt(2) and sqrt(5) together again.

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