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Question Number 86657 by john santu last updated on 30/Mar/20
solve (1+x^3 )dy −x^2  y dx=0  y(1) = 2
$$\mathrm{solve}\:\left(\mathrm{1}+\mathrm{x}^{\mathrm{3}} \right)\mathrm{dy}\:−\mathrm{x}^{\mathrm{2}} \:\mathrm{y}\:\mathrm{dx}=\mathrm{0} \\ $$$$\mathrm{y}\left(\mathrm{1}\right)\:=\:\mathrm{2} \\ $$
Answered by jagoll last updated on 30/Mar/20
∫ (dy/y) = ∫ (x^2 /(1+x^3 )) dx  ln y = (1/3)lnC(1+x^3 ) = ln((C(1+x^3 )))^(1/(3  ))   y = ((C(1+x^3 )))^(1/(3  ))   y(1) = 2 ⇒ 2 = ((2C))^(1/(3  ))   8 = 2C ⇒C = 4  ∴ y = ((4+4x^3 ))^(1/(3 ))
$$\int\:\frac{\mathrm{dy}}{\mathrm{y}}\:=\:\int\:\frac{\mathrm{x}^{\mathrm{2}} }{\mathrm{1}+\mathrm{x}^{\mathrm{3}} }\:\mathrm{dx} \\ $$$$\mathrm{ln}\:\mathrm{y}\:=\:\frac{\mathrm{1}}{\mathrm{3}}\mathrm{lnC}\left(\mathrm{1}+\mathrm{x}^{\mathrm{3}} \right)\:=\:\mathrm{ln}\sqrt[{\mathrm{3}\:\:}]{\mathrm{C}\left(\mathrm{1}+\mathrm{x}^{\mathrm{3}} \right)} \\ $$$$\mathrm{y}\:=\:\sqrt[{\mathrm{3}\:\:}]{\mathrm{C}\left(\mathrm{1}+\mathrm{x}^{\mathrm{3}} \right)} \\ $$$$\mathrm{y}\left(\mathrm{1}\right)\:=\:\mathrm{2}\:\Rightarrow\:\mathrm{2}\:=\:\sqrt[{\mathrm{3}\:\:}]{\mathrm{2C}} \\ $$$$\mathrm{8}\:=\:\mathrm{2C}\:\Rightarrow\mathrm{C}\:=\:\mathrm{4} \\ $$$$\therefore\:\mathrm{y}\:=\:\sqrt[{\mathrm{3}\:}]{\mathrm{4}+\mathrm{4x}^{\mathrm{3}} } \\ $$
Commented by john santu last updated on 30/Mar/20
joosss
$$\mathrm{joosss} \\ $$

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