Recent content by Damned charming :)

Mathematica cannot seem to do it, It can solve y'' = 1/y The solution is e to the power of a complicated function of the Inverse of the intergral of e^-(x^2) I cannot see how multiplying by x^3 would make it easier. I would bet a reasonable sum of money on it being a misprint.

I feel quite silly for not noticing the differential equations forum, How do I get this thread moved.

you can use a t test just like you do in simple linear regression, except the degrees of freedom is n-3 not n-2, You can test each variable separately. you have to be careful about any conlcusions you make for example if x1 and x2 are highly correlated.

I saw a first year question solve y''=x^3/y I am assuming that this is a misprint because solving y'= x^3/y is easy because it is separable but I have no idea how to solve y'' = x^3/y

Thanks for this guys I thought I was going mad. Fancy 2 books being wrong.

a car of mass m is traveling around a banked track. if F is the friction force up the track and x is the angle of the track I say F= mg sin(x)- mv^2/r cos(x) N = mg cos(x) + mv^2/r sin(x) but both my books say F= mg sin(x)- mv^2/r cos(x) N = mg cos(x) - mv^2/r sin(x)

I am teaching a student in a course without partial differentiation so I can only think of the following method let b be a constant and set y=b so xb= exp(x-1) +blnb means b= exp(x-1) which means x = lnb+1 now d(xb)/dx= b and d(exp(x-1)+blnb)/dx = exp(x-1) so if x > lnb+1 xb>...

Every australian university I know basically forces most students to deal with the topics in this thread in first year.

Gokul I am embarassed at my typos, I will fix them As for the dilema of students being used to only have one answer, If you if you are in R3 and say x=0 you can ask the students what values y and z can take and they don't know, when you say y and z can take any value they don't believe you...

Does anyone have sample wrong answers for the multiple choice test I was writing in the first post? I offer a warning to people that will teach that subject. The that bottom half of the class does not believe you initially when you say x=0 is a plane in R3. The idea that y and z can take any...

OK I will explain the questions to prove I am not a liar x+y=5 can be represented in RREF as (1 1 |5) y is a non leading varible ( a free variable) let y =t so x+ t = 5 x=5-t to summarize) (x,y) = (5-t , t) this is the same as (x,y) = (5,0) + (-1,1)t This a line in R2 Moving on to...

Ask me hard question so I can prove my credentials please.

I teach first year uni students and they don't seem to know what is a plane and what is a line in 3d. I have been paid to make an online multiple choice a prototype is given below. Any help would be appreciated 1)x+y=5 (a) has infinite solutions examples of solutions are (-1,6), (0,5)...

You only need to prove that appling simpsons rule to x^3 gives the same answer as integration. Thi It should be clear that if simpsons works for both polynomials p(x) and q(x) then it works for p(x)+ q(x). Because int (p(x)+q(x)) = int(p(x)) + int(q(x)) and the same rule applies to...

sin(x)/cos(x) = tan(x) to see why this is true Draw a right triangle with hypotenuse 1 and an acute angle x, you can work the sides of the right triangle have lengths sin(x) and cos(x).