Given differential equation isd y d x + ( − 3 x 5 tan − 1 ( x 3 ) ( 1 + x 6 ) 3 / 2 ) y = 2 x e { x 3 − tan − 1 x 3 ( 1 + x ) 6 } \dfrac{dy}{dx} + \left(\dfrac{- 3{x}^{5}\tan^{- 1}\left({x}^{3}\right)}{{\left(1 + {x}^{6}\right)}^{3 / 2}}\right)y = 2x{e}^{\left\{\dfrac{{x}^{3} - \tan^{- 1}{x}^{3}}{\sqrt{{\left(1 + x\right)}^{6}}}\right\}} d x d y + ( ( 1 + x 6 ) 3/2 − 3 x 5 tan − 1 ( x 3 ) ) y = 2 x e { ( 1 + x ) 6 x 3 − t a n − 1 x 3 }
This is a linear differential equation of the form d y d x + P y = Q \dfrac{dy}{dx} + Py = Q d x d y + P y = Q .
Hence,
I . F . = e ∫ − 3 x 5 tan − 1 x 3 ( 1 + x 6 ) 3 / 2 d x I . F . = {e}^{∫ \dfrac{- 3{x}^{5}\tan^{- 1}{x}^{3}}{{\left(1 + {x}^{6}\right)}^{3 / 2}}dx} I . F . = e ∫ ( 1 + x 6 ) 3/2 − 3 x 5 t a n − 1 x 3 d x
Put tan − 1 x 3 = u ⇒ ( 3 x 2 1 + x 6 ) d x = d u \tan^{- 1}{x}^{3} = u ⇒ \left(\dfrac{3{x}^{2}}{1 + {x}^{6}}\right)dx = du tan − 1 x 3 = u ⇒ ( 1 + x 6 3 x 2 ) d x = d u
I . F . = e − ∫ u t a n u 1 + tan 2 u d u I . F . = {e}^{- ∫ \dfrac{utanu}{\sqrt{1 + \tan^{2}u}}du} I . F . = e − ∫ 1 + t a n 2 u u t an u d u
⇒ I . F . = e − ∫ u t a n u sec u d u ⇒ I . F . = {e}^{- ∫ \dfrac{utanu}{\sec u}du} ⇒ I . F . = e − ∫ s e c u u t an u d u
⇒ I . F . = e − ∫ u s i n u d u ⇒ I . F . = {e}^{- ∫ usinudu} ⇒ I . F . = e − ∫ u s in u d u
⇒ I . F . = e − [ − u c o s u + ∫ c o s u d u ] ⇒ I . F . = {e}^{- \left[- ucosu + ∫ cosudu\right]} ⇒ I . F . = e − [ − u cos u + ∫ cos u d u ]
⇒ I . F . = e u c o s u − sin u ⇒ I . F . = {e}^{ucosu - \sin u} ⇒ I . F . = e u cos u − s i n u
⇒ I . F . = e { tan − 1 ( x 3 ) ( 1 1 + x 6 ) − ( x 3 1 + x 6 ) } ⇒ I . F . = {e}^{\left\{\tan^{- 1}\left({x}^{3}\right)\left(\dfrac{1}{\sqrt{1 + {x}^{6}}}\right) - \left(\dfrac{{x}^{3}}{\sqrt{1 + {x}^{6}}}\right)\right\}} ⇒ I . F . = e { t a n − 1 ( x 3 ) ( 1 + x 6 1 ) − ( 1 + x 6 x 3 ) }
⇒ I . F . = e { tan − 1 x 3 − x 3 1 + x 6 } ⇒ I . F . = {e}^{\left\{\dfrac{\tan^{- 1}{x}^{3} - {x}^{3}}{\sqrt{1 + {x}^{6}}}\right\}} ⇒ I . F . = e { 1 + x 6 t a n − 1 x 3 − x 3 }
Solution of differential equation is
y ⋅ e tan − 1 x 3 − x 3 1 + x 6 = ∫ 2 x e ( x 3 − tan − 1 x 3 1 + x 6 ) ⋅ e ( tan − 1 ( x 3 ) − x 3 1 + x 6 ) d x y \cdot e\dfrac{\tan^{- 1}{x}^{3} - {x}^{3}}{\sqrt{1 + {x}^{6}}} = ∫ 2x{e}^{\left(\dfrac{{x}^{3} - \tan^{- 1}{x}^{3}}{\sqrt{1 + {x}^{6}}}\right)} \cdot {e}^{\left(\dfrac{\tan^{- 1}\left({x}^{3}\right) - {x}^{3}}{\sqrt{1 + {x}^{6}}}\right)}dx y ⋅ e 1 + x 6 tan − 1 x 3 − x 3 = ∫ 2 x e ( 1 + x 6 x 3 − t a n − 1 x 3 ) ⋅ e 1 + x 6 t a n − 1 ( x 3 ) − x 3 d x
⇒ y ⋅ e { tan − 1 x 3 − x 3 1 + x 6 } = ∫ 2 x d x ⇒ y \cdot {e}^{\left\{\dfrac{\tan^{- 1}{x}^{3} - {x}^{3}}{\sqrt{1 + {x}^{6}}}\right\}} = ∫ 2xdx ⇒ y ⋅ e { 1 + x 6 t a n − 1 x 3 − x 3 } = ∫ 2 x d x
⇒ y ⋅ e { tan − 1 x 3 − x 3 1 + x 6 } = x 2 + C ⇒ y \cdot {e}^{\left\{\dfrac{\tan^{- 1}{x}^{3} - {x}^{3}}{\sqrt{1 + {x}^{6}}}\right\}} = {x}^{2} + C ⇒ y ⋅ e { 1 + x 6 t a n − 1 x 3 − x 3 } = x 2 + C
Also, it passes through the origin then C = 0 C = 0 C = 0 , hence
y e { tan − 1 x 3 − x 3 1 + x 6 } = x 2 y{e}^{\left\{\dfrac{\tan^{- 1}{x}^{3} - {x}^{3}}{\sqrt{1 + {x}^{6}}}\right\}} = {x}^{2} y e { 1 + x 6 t a n − 1 x 3 − x 3 } = x 2
Now, put x = 1 x = 1 x = 1 , then we get
y ( 1 ) e tan − 1 ( 1 ) − 1 2 = 1 y\left(1\right)e\dfrac{\tan^{- 1}\left(1\right) - 1}{\sqrt{2}} = 1 y ( 1 ) e 2 tan − 1 ( 1 ) − 1 = 1
⇒ y ( 1 ) e π − 4 4 2 = 1 ⇒ y\left(1\right)e\dfrac{\pi - 4}{4\sqrt{2}} = 1 ⇒ y ( 1 ) e 4 2 π − 4 = 1
⇒ y ( 1 ) = 1 e ( π − 4 4 2 ) ⇒ y\left(1\right) = \dfrac{1}{{e}^{\left(\dfrac{\pi - 4}{4\sqrt{2}}\right)}} ⇒ y ( 1 ) = e ( 4 2 π − 4 ) 1
⇒ y ( 1 ) = e 4 − π 4 2 ⇒ y\left(1\right) = e\dfrac{4 - \pi}{4\sqrt{2}} ⇒ y ( 1 ) = e 4 2 4 − π