Câu trả lời:

ta có: B=1/4^2 +1/6^2+......+1/200^2

        B= 1/2^2 x(1/2^2+1/3^2 +1/4^2+......+1/100^2)

        B=1/4 x(A)

suy ra: A/B= A / 1/4 x A

          A/B= 4