The given equation is a separable equation of the form f ( x , p ) = g ( y , q ) f(x, p)=g(y, q) f ( x , p ) = g ( y , q ) .
The complete solution will be, z = ∫ p d x + ∫ q d y + c z = \int pdx + \int qdy + c z = ∫ p d x + ∫ q d y + c
Let f ( x , p ) = g ( y , q ) = a f(x, p)=g(y, q) =a f ( x , p ) = g ( y , q ) = a . Solving for f ( x , p ) = a & g ( y , q ) = a f(x, p)=a~ \&~ g(y, q) =a f ( x , p ) = a & g ( y , q ) = a , we get
p − 3 x 2 = a ; q 2 − y = a p = 3 x 2 + a ; q 2 = y + a p = 3 x 2 + a ; q = y + a \begin{aligned}
p-3x^2 &= a&; & ~q^2 -y = a\\
p&=3x^2 + a&; & ~q^2=y+a\\
p&=3x^2 + a&; & ~q=\sqrt{y+a}\\
\end{aligned} p − 3 x 2 p p = a = 3 x 2 + a = 3 x 2 + a ; ; ; q 2 − y = a q 2 = y + a q = y + a
The complete solution is,
z = ∫ p d x + ∫ q d y + c z = ∫ ( 3 x 2 + a ) d x + ∫ ( y + a ) d y + c = x 3 + a x + 2 3 ( y + a ) 3 2 + c \begin{aligned}
z &= \int pdx + \int qdy + c\\
z &= \int (3x^2 + a)dx + \int (\sqrt{y+a})dy + c\\
&= x^{3} + ax + \frac{2}{3}(y+a)^{\frac{3}{2}} + c
\end{aligned} z z = ∫ p d x + ∫ q d y + c = ∫ ( 3 x 2 + a ) d x + ∫ ( y + a ) d y + c = x 3 + a x + 3 2 ( y + a ) 2 3 + c
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