# Homework Help: 2nd order d.e

1. Aug 30, 2008

### fredrick08

1. The problem statement, all variables and given/known data
x"=(-1/x^2) when x=c1>0 and x'=c2 at t=0 what relationship has to exist between c1 and c2 to give the problem a solution of k(t+B)^a.... then solve for k,a,B....

3. The attempt at a solution
x"+(1/x^2)=0, im sorry im just stuck, i think it goin to look somthin like (x+2)^2.... but this inverse square is confusing me... we normally do it like,

$$\lambda$$"+a$$\lambda$$=0, but im not sure, can anyone plz point me in the right direction.... but then wat does it mean by what relationship between c1and c2?

2. Aug 31, 2008

### HallsofIvy

The first thing you need to do is state the problem clearly. " x"= -1/x2 when x= c1> 0" only gives x" at a single value of x. Did you mean "for x> c1"?

Rewrite the equation as x2x"= -x and see what happens when you replace x with k(t+B)a.

3. Aug 31, 2008

### fredrick08

na thats wat the question says... its definately x=c1>0..... huh i cant write it like that coz then it would be (x^2)x"=-1 not -x.... wel doesnt that mean that c1=c2???