- #1
Deathfish
- 86
- 0
Homework Statement
Original problem is differential equation dy/dx=(x+2y)/(3y-2x)
This is part of solving differential equation.
x(dv/dx) = (1+4v-3v^2)/(3v-2)
so one way of solving, I take out the negative sign
x(dv/dx) = -((3v^2-4v-1)/(3v-2)) , separate and bring over
-∫((3v-2)/(3v^2-4v-1)) dv = ∫1/x dx
which gets me
-(1/2)ln(3v^2-4v-1)=ln(x)+C
however, if i don't take out negative sign,
x(dv/dx) = (1+4v-3v^2)/(3v-2), separate and bring over
∫((3v-2)/(1+4v-3v^2)) = ∫1/x dx
which gets me
-(1/2)ln(-3v^2+4v+1)=ln(x)+C result is opposite sign from above.
checked again and again and i can't seem to find out why even though the working seems ok, the answer is very different...
i get 3y^2-4yx-x^2=C for one method
and x^2+4xy-3y^2=C for the other method
Last edited: