7.7.3 2.3

7.7.3.1 [1599] Problem 1

problem number 1599

Added June 1, 2019.

Problem Chapter 7.2.3.1, from Handbook of first order partial differential equations by Polyanin, Zaitsev, Moussiaux.

Solve for \(w(x,y,z)\)

\[ w_x + a w_y + b w_z = x y z \]

Mathematica ✓

ClearAll["Global`*"]; 
pde =  D[w[x, y,z], x] + a*D[w[x, y,z], y] +b*D[w[x,y,z],z]==x*y*z; 
sol =  AbsoluteTiming[TimeConstrained[DSolve[pde, w[x, y,z], {x, y,z}], 60*10]];
 

\[\left \{\left \{w(x,y,z)\to \frac {1}{12} x^2 (a x (b x-2 z)-2 b x y+6 y z)+c_1(y-a x,z-b x)\right \}\right \}\]

Maple ✓

restart; 
local gamma; 
pde := diff(w(x,y,z),x)+ a*diff(w(x,y,z),y)+b*diff(w(x,y,z),z)=x*y*z; 
cpu_time := timelimit(60*10,CodeTools[Usage](assign('sol',pdsolve(pde,w(x,y,z))),output='realtime'));
 

\[w \left (x , y , z\right ) = \frac {a b \,x^{4}}{12}+\frac {x^{2} y z}{2}+\frac {\left (-2 a z -2 b y \right ) x^{3}}{12}+\textit {\_F1} \left (-a x +y , -b x +z \right )\]

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7.7.3.2 [1600] Problem 2

problem number 1600

Added June 1, 2019.

Problem Chapter 7.2.3.2, from Handbook of first order partial differential equations by Polyanin, Zaitsev, Moussiaux.

Solve for \(w(x,y,z)\)

\[ a w_x + b w_y + c w_z = k x^3+s y^2 \]

Mathematica ✓

ClearAll["Global`*"]; 
pde =  a*D[w[x, y,z], x] + b*D[w[x, y,z], y] +c*D[w[x,y,z],z]==k*x^3+s*y^2; 
sol =  AbsoluteTiming[TimeConstrained[DSolve[pde, w[x, y,z], {x, y,z}], 60*10]];
 

\[\left \{\left \{w(x,y,z)\to \frac {x \left (3 a^2 \left (k x^3+4 s y^2\right )-12 a b s x y+4 b^2 s x^2\right )}{12 a^3}+c_1\left (y-\frac {b x}{a},z-\frac {c x}{a}\right )\right \}\right \}\]

Maple ✓

restart; 
local gamma; 
pde := a*diff(w(x,y,z),x)+ b*diff(w(x,y,z),y)+c*diff(w(x,y,z),z)=k*x^3+s*y^2; 
cpu_time := timelimit(60*10,CodeTools[Usage](assign('sol',pdsolve(pde,w(x,y,z))),output='realtime'));
 

\[w \left (x , y , z\right ) = \frac {k \,x^{4}}{4 a}+\frac {s x \,y^{2}}{a}-\frac {b s \,x^{2} y}{a^{2}}+\frac {b^{2} s \,x^{3}}{3 a^{3}}+\textit {\_F1} \left (\frac {a y -b x}{a}, \frac {a z -c x}{a}\right )\]

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7.7.3.3 [1601] Problem 3

problem number 1601

Added June 1, 2019.

Problem Chapter 7.2.3.3, from Handbook of first order partial differential equations by Polyanin, Zaitsev, Moussiaux.

Solve for \(w(x,y,z)\)

\[ a w_x + b y w_y + c z w_z = k x+ s \sqrt x \]

Mathematica ✓

ClearAll["Global`*"]; 
pde =  a*D[w[x, y,z], x] + b*y*D[w[x, y,z], y] +c*z*D[w[x,y,z],z]==k*x+s*Sqrt[x]; 
sol =  AbsoluteTiming[TimeConstrained[DSolve[pde, w[x, y,z], {x, y,z}], 60*10]];
 

\[\left \{\left \{w(x,y,z)\to \frac {6 a c_1\left (y e^{-\frac {b x}{a}},z e^{-\frac {c x}{a}}\right )+3 k x^2+4 s x^{3/2}}{6 a}\right \}\right \}\]

Maple ✓

restart; 
local gamma; 
pde := a*diff(w(x,y,z),x)+ b*y*diff(w(x,y,z),y)+c*z*diff(w(x,y,z),z)=k*x+s*sqrt(x); 
cpu_time := timelimit(60*10,CodeTools[Usage](assign('sol',pdsolve(pde,w(x,y,z))),output='realtime'));
 

\[w \left (x , y , z\right ) = \frac {k \,x^{2}}{2 a}+\frac {2 s \,x^{\frac {3}{2}}}{3 a}+\textit {\_F1} \left (y \,{\mathrm e}^{-\frac {b x}{a}}, z \,{\mathrm e}^{-\frac {c x}{a}}\right )\]

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7.7.3.4 [1602] Problem 4

problem number 1602

Added June 1, 2019.

Problem Chapter 7.2.3.4, from Handbook of first order partial differential equations by Polyanin, Zaitsev, Moussiaux.

Solve for \(w(x,y,z)\)

\[ w_x + a z w_y + b y w_z = c \sqrt x + s \]

Mathematica ✓

ClearAll["Global`*"]; 
pde =  D[w[x, y,z], x] + a*z*D[w[x, y,z], y] +b*y*D[w[x,y,z],z]==c*Sqrt[x]+s; 
sol =  AbsoluteTiming[TimeConstrained[DSolve[pde, w[x, y,z], {x, y,z}], 60*10]];
 

\[\left \{\left \{w(x,y,z)\to c_1\left (\frac {e^{-\sqrt {a} \sqrt {b} x} \left (\sqrt {b} y \left (e^{2 \sqrt {a} \sqrt {b} x}+1\right )-\sqrt {a} z \left (e^{2 \sqrt {a} \sqrt {b} x}-1\right )\right )}{2 \sqrt {b}},\frac {e^{-\sqrt {a} \sqrt {b} x} \left (\sqrt {a} z \left (e^{2 \sqrt {a} \sqrt {b} x}+1\right )-\sqrt {b} y \left (e^{2 \sqrt {a} \sqrt {b} x}-1\right )\right )}{2 \sqrt {a}}\right )+\frac {2}{3} c x^{3/2}+s x\right \}\right \}\]

Maple ✓

restart; 
local gamma; 
pde := diff(w(x,y,z),x)+ a*z*diff(w(x,y,z),y)+b*y*diff(w(x,y,z),z)=c*sqrt(x)+s; 
cpu_time := timelimit(60*10,CodeTools[Usage](assign('sol',pdsolve(pde,w(x,y,z))),output='realtime'));
 

\[w \left (x , y , z\right ) = \int _{}^{y}\frac {\sqrt {\frac {\sqrt {a b}\, x +\ln \left (\frac {\textit {\_a} a b +\sqrt {\left (a \,z^{2}+\left (\textit {\_a}^{2}-y^{2}\right ) b \right ) a}\, \sqrt {a b}}{\sqrt {a b}}\right )-\ln \left (\frac {a b y +\sqrt {a^{2} z^{2}}\, \sqrt {a b}}{\sqrt {a b}}\right )}{\sqrt {a b}}}\, c +s}{\sqrt {\left (a \,z^{2}+\left (\textit {\_a}^{2}-y^{2}\right ) b \right ) a}}d \textit {\_a} +\textit {\_F1} \left (\frac {a \,z^{2}-b \,y^{2}}{a}, -\frac {-\sqrt {a b}\, x +\ln \left (\frac {a b y +\sqrt {a^{2} z^{2}}\, \sqrt {a b}}{\sqrt {a b}}\right )}{\sqrt {a b}}\right )\]

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7.7.3.5 [1603] Problem 5

problem number 1603

Added June 1, 2019.

Problem Chapter 7.2.3.5, from Handbook of first order partial differential equations by Polyanin, Zaitsev, Moussiaux.

Solve for \(w(x,y,z)\)

\[ a x^2 w_x + b y^2 w_y + c z^2 w_z = k x y z \]

Mathematica ✓

ClearAll["Global`*"]; 
pde =  a*x^2*D[w[x, y,z], x] + b*y^2*D[w[x, y,z], y] +c*z^2*D[w[x,y,z],z]==k*x*y*z; 
sol =  AbsoluteTiming[TimeConstrained[DSolve[pde, w[x, y,z], {x, y,z}], 60*10]];
 

\[\left \{\left \{w(x,y,z)\to \frac {k x y z \left (b y (a x-c z) \log \left (\frac {a x}{y}\right )+c z (b y-a x) \log \left (\frac {a x}{z}\right )\right )}{(a x-b y) (a x-c z) (b y-c z)}+c_1\left (\frac {b}{a x}-\frac {1}{y},\frac {c}{a x}-\frac {1}{z}\right )\right \}\right \}\]

Maple ✓

restart; 
local gamma; 
pde := a*x^2*diff(w(x,y,z),x)+b*y^2*diff(w(x,y,z),y)+c*z^2*diff(w(x,y,z),z)=k*x*y*z; 
cpu_time := timelimit(60*10,CodeTools[Usage](assign('sol',pdsolve(pde,w(x,y,z))),output='realtime'));
 

\[w \left (x , y , z\right ) = \frac {\left (\left (a x -c z \right ) b y \ln \left (\frac {a x}{y}\right )-\left (a x -b y \right ) c z \ln \left (\frac {a x}{z}\right )\right ) k x y z +\left (b y -c z \right ) \left (a x -c z \right ) \left (a x -b y \right ) \textit {\_F1} \left (\frac {a x -b y}{a x y}, \frac {a x -c z}{a x z}\right )}{\left (b y -c z \right ) \left (a x -c z \right ) \left (a x -b y \right )}\]

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