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D2y/dx2+1/xdy/dx=12 logx/x^2 |
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Answer» Answer: d2ydx2+1xdydx=12ln|x|x2 x2d2ydx2+xdydx=12ln|x| Let us start with the homogeneous equation; x2d2ydx2+xdydx=0 Now you can realise this is the Euler Cauchy equation which shows the transformation; x2d2ydx2+bxdydx+cy=0 Using x=etTransforms into; d2ydt2+(b−1)dydt+cy=0 And this equation has the auxiliary equation as; r2+(b−1)r+c=0 And after solving this equation, and substituting back the three possible types of solutions are; y=⎧⎩⎨⎪⎪c1|x|R1+c2|x|r2,|x|r(c1+c2ln|x|),|x|a(c1cos(bln|x|)+c2sin(bln|x|)),if the auxiliary equation as TWO distinct real roots r1,r2if the auxiliary equation has two equal roots r,if the auxiliary equation has two complex roots a±bi⎫⎭⎬⎪⎪ So our equation; x2d2ydx2+xdydx=0 becomes; d2ydt2+(1−1)dydt=0 d2ydt2=0 The auxiliary equation is; r2=0→r=0 So the SOLUTION to the ORIGINAL homogeneous equation is; y=|x|0(c1+c2ln|x|) y=c1+c2ln|x|, this is your complementary function. Now let's look for the particular integral for; x2d2ydx2+xdydx=12ln|x| Let y=a(ln|x|)b dydx=ab(ln|x|)b−1x d2ydx2=ab(x(b−1)(ln|x|)b−2x−(ln|x|)b−1x2) Replacing this in our differential equation; ab(b−1)(ln|x|)b−2−ab(ln|x|)b−1+ab(ln|x|)b−1=12ln|x| ab(b−1)(ln|x|)b−2=12ln|x| b−2=1→b=3 ab(b−1)=12→a=2 So particular integral is; 2(ln|x|)3 And so the solution to the second order differential equation d2ydx2+1xdydx=12ln|x| is ; y=c1+c2ln|x|+2(ln|x|)3 Explanation: HERE U GO HAVE A GOOD DAY MATE!! |
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