Maths Help (Differential Equations)

[acroviak]

Hey.

Stuck on some maths work on differential equations.

Pretty basic stuff, but its late and i can't seem to get my head around it.

Heres the two i can't do.

1. Find solution of dy/dx = 3x^2 - 4x which passes through (1,1)

2. Write general solution of dy/dx = x^2 e^x^3

thanks!

[mohill]

I am sufficiently ignorant that I don't know how to show the squared sign.
No1 dy/dx = 3x(sq) - 4x
Integrate
y = x(cub) - 2x(sq) + k
This curve passes through (1,1)
So substituting, we have 1 = 1(cubed) -2 times 1(sq) + k
1 = 1 - 2 + K
K = 2
so solution is y = x(cub) - 2x + 2

[johnalex]

Well done mohill - try this:

Alt 253 = ²
Alt 251 = √
Alt 228 = Σ
. . . and so on (there are 256 characters in the standard set)

You need to hold down the Alt Key, then enter the character code on your number pad (not the ones above QWERTY). Laptoppers have to press a function key then use the coloured numbers on their text keyboard, so I believe.

Let us know how you get on!

[mohill]

Thank you johnalex! Much appreciated. I have not yet tried it but I see that if I try alt in the 200s I should be able locate what i might ever need.

Thanks also for your encouraging comment.
Cheers!