Thread: One calculus questions

Just one question I did not understand on my calculus worksheet.

If y= 3/4+x^2 then dy/dx = ?

3/2x?

Hey fancy shoers

That looks like a typo to me - the question should read

If y= 3/4*x^2 then dy/dx = ?

Well IF Y = 0.75 X^2 then dy/dx= 1.5x which is the same.

Rare for me to post in maths, but I'll make an exception, I agree with RR.

its actually this. sorry i did not put brackets if y=3/(4+x^2) then dy/dx = ?

Originally Posted by FancyShoes

its actually this. sorry i did not put brackets if y=3/(4+x^2) then dy/dx = ?

Set z = 4 + x². What is dz/dx? Show you are trying, even if its wrong

Ah use the quotient rule or the chain rule - what ever you feel more comfortable with really. Your answer is definitely not correct btw.

differentiate it from first principles (if you are not yet familiar with Quotient/chain) - it'll be good practice anyway.

let's say f(x) = 1/(5x+3)

I wrote that one out on paper, I don't know where all the maths symbols are but I got

dy/dx = -5/(5x+3)^2

River rat will tell if I've made a balls up.....

It looks like homework though, so you'll have to do it yourself,

Looks fine to me Megabrain - though doing the original question by first principles looks very hairy!

ya I went and asked my teacher answer was 6x/(4+x^2)^2 if anyone wanted to know. Ya he told me to use the chain rule

Originally Posted by FancyShoes

ya I went and asked my teacher answer was 6x/(4+x^2)^2 if anyone wanted to know. Ya he told me to use the chain rule

I hope he did not say that 6x/(4+x^2)^2 was the answer! Eish.