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b, Đặt (C_1): y=x^2, \quad(C_2): y=x^2/8, \quad(C_3): y=8/x, \quad
Ta có:
(C_1) \cap (C_2) : x^2=x^2/8 \Leftrightarrow x=0
(C_3) \cap (C_2) : 8/x=x^2/8 \Leftrightarrow x=4
(C_1) \cap (C_3) : x^2=8/x \Leftrightarrow x=2
Diện tích hình cần tìm là:
S=\int\limits_{0}^{2}\left| { x^2-x^2/8} \right|dx+\int\limits_{2}^4\left| { 8/x-x^2/8} \right|dx
=\int\limits_{0}^{2}7x^2/8dx+\int\limits_{2}^4(8/x-x^2/8)dx
=\dfrac{7}{3} +8\ln 2-\dfrac{7}{3} =8\ln 2
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