Using Product Rule to Transform Equations A to B: Understanding the Process

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SUMMARY

The transformation from equation A to equation B involves the application of the product rule in calculus. Starting with equation A, D(1/r^2)d/dr(r^2(dC/dr))-kC=0, the product rule is utilized to differentiate r^2(dC/dr), resulting in r^2(d^2C/dr^2) + 2r(dC/dr). This leads to the simplified form d^2C/dr^2 + (2/r)(dC/dr) - (kC)/D = 0, which is equation B. The final step involves dividing the entire equation by D to achieve the desired format.

PREREQUISITES
  • Understanding of calculus, specifically the product rule
  • Familiarity with differential equations
  • Knowledge of variable separation techniques
  • Basic understanding of physical constants and their roles in equations
NEXT STEPS
  • Study the product rule in calculus for differentiation techniques
  • Learn about solving second-order differential equations
  • Explore variable separation methods in differential equations
  • Investigate the role of physical constants in mathematical modeling
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Students and professionals in mathematics, physics, and engineering who are working with differential equations and require a deeper understanding of transformation techniques in mathematical modeling.

juice34
My question is how do they transform equation A. into B.. I know they are using the product rule but don't know what is going on.

EQ A.)D(1/r^2)d/dr(r^2(dC/dr))-kC=0
now how do they get Eq B.

EQ B.) (d^2C/dr^2)+(2/r)(dC/dr)-(kC)/D=0
 
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juice34 said:
My question is how do they transform equation A. into B.. I know they are using the product rule but don't know what is going on.

EQ A.)D(1/r^2)d/dr(r^2(dC/dr))-kC=0
now how do they get Eq B.

EQ B.) (d^2C/dr^2)+(2/r)(dC/dr)-(kC)/D=0
The derivative of r^2 dC/dr is, by the product rule, [r^2 d(dC/dr)/dr]+ [d(r^2)/dr] dC/dr= r^2 d^2C/dr+ 2r dC/dr. Multiplying that by 1/r^2 gives d^2C/dr^2+ 2/r dC/dr so the equation is the same as D(d^2C/dr^2+ 2/r dC/dr)- kC= 0.

Dividing the entire equation by D, then, gives eq. B.
 

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