# Recent content by justinis123

1. ### Laplace transform

thanks for reply, after i solve partial fraction what should i do? I solved: which = 3/40s + ((-3s/40-3/2))/(s^2+20s+200)
2. ### Laplace transform

I can get 150/s * 1/((s+10)^2+10^2), but this dosent seems to fit either sin or cos
3. ### Laplace transform

U mean use partial fractions on s(s^2+20s+200)? but how?
4. ### Laplace transform

Homework Statement I already got Q(s)=150/(s(s^2+20s+200)), then i complete the square on the quadratic. I got Q(s)=150/(s((s+10)^2+10^2))). But then i cant find the Q(t) because the equation (s+10)^2+10^2=0 dosent have roots. Or i have to use complex numbers ? So I am confused. Homework...
5. ### Find the general solution

Homework Statement Find the general solution of: dy/dx=lnx/(xy+xy^3) Homework Equations The Attempt at a Solution In order to find the general solution, i rerrange the equation to:(y+y^3)dy=(lnx/x)dx, then int(y+y^3)dy=int(lnx/x)dx, then i got 2(lnx)^2=2y^2+y^4. then i rerange y...
6. ### Differentiation the integral

Thanks , i see the problem. I fixed the issue and got the right answer.
7. ### Differentiation the integral

Hi uart Thanks for the reply. Yeah, that was a typo. It should be 2x^2 as you assumed. what do u mean by using product rule to find f' ? f'(x)=xsin(x^2), then using product rule to find f''(x)=sin(x^2) + 2x^2 cos(x^2). Could you please show me how to find f'(x)? I am a bit confused. thanks
8. ### Differentiation the integral

Homework Statement Let f (x) =int(x,0) x sin(t^2)dt. Show that f''(x)= 2 sin(x^2) + 2x2 cos(x^2) Homework Equations The Attempt at a Solution I cant get f''(x)= 2 sin(x^2) + 2x2 cos(x^2), i can only get f''(x)= sin(x^2) + 2x2 cos(x^2). Because f'(x)=xsin(x^2). can anyone see...