Core pure 2 question, need help

Last Post

Posts: 115

Usman

LSC Tutor

Topic starter

Jun 07, 2020 5:17 pm

(@usman)

Estimable Member

Joined: 4 years ago

How would you do this question?

2 Replies

Posts: 272

Further_Maths_Student

ExamQA+

Jun 07, 2020 10:05 pm

(@further_maths_student)

Reputable Member

Joined: 4 years ago

Are you stuck in approaching the question or a particular part of it

Posts: 53

Tye

Jun 07, 2020 11:00 pm

(@tye)

Trusted Member

Joined: 3 years ago

Basically we should never have x coefficients in front of the d2y/dx2 or dy/dx, they should only be numbers right?

So the question wants you to use that x = e^u substitution to get rid of the x^2 and x for the time being. To do that, you must basically find out dy/du and dy2/du2 - when you do that you can basically form a differential equation with no x coefficeients.

This is because because y is a function of x and x is a function of u, that means y is a function of u

And so are all the derivatives

I.e. y(x) = y(x(u))

And when we talk about it's derivatives you should use the chain rule

so y'(x) = dy/dx * dx/du

After you get rid of the x^2 and x in front of the derivatives it becomes a normal differential equations question