What?!

Ok, i have maths homework in for tomorrow, can anyone do differentiation? (obviously i haven't quite perfected technique yet);

i need to find dy/dx when y= (116-21x^2) divided by 120.

Anyclues?

Reply 1

boygenious

CoraBelle

Ok, i have maths homework in for tomorrow, can anyone do differentiation? (obviously i haven't quite perfected technique yet);

i need to find dy/dx when y= (116-21x^2) divided by 120.

Anyclues?

i'm pretty sure it's just -42x/120 = -7x/20

Reply 2

CoraBelle

boygenious

i'm pretty sure it's just -42x/120 = -7x/20

Thanks so much, yup thats what is said.. i see it now they just cancelled down...

I don't suppose you would be able to explain how you would find the point on a curve which is parrellel to a line?

How woud you know if a line was a tangent to a curve?

Sorry for all these questions - our teachers going mega fast through this and i'm more of a slow learner myself!

thanks anyhow!
Love CoraBelle

Reply 3

sili-Kate

CoraBelle

Hey

When the curve is parallel to the line then the gradients are equal, so dy/dx are equal and then you can work out x.

similar thing for if a line is a tangent to the curve. the tangent and the line have the same gradient so dy/dx is equal!

Sorry that was a bit brief. Hope it helps

Reply 4

john !!

CoraBelle

Ok, i have maths homework in for tomorrow, can anyone do differentiation? (obviously i haven't quite perfected technique yet);

i need to find dy/dx when y= (116-21x^2) divided by 120.

Anyclues?

y = (116-21x^2)/120
= 116/120 - (21/210)x^2
dy/dx = -2(21/210)x
= -5x

Reply 5

Unregistered

whatever mik1a says, goes.

Reply 6

Ally45

unfortunately not everything mik1a says goes... hes just plain wrong. that is not how you differentiate that function. this first reply was perfectly correct. look again mik1a and dazya

Reply 7

lgs98jonee

Ally45

unfortunately not everything mik1a says goes... hes just plain wrong. that is not how you differentiate that function. this first reply was perfectly correct. look again mik1a and dazya

what? please explain this to me sum1

Reply 8

hitchhiker_13

I am perturbed by the fact that 2 different answers are given.
Nothing upsets me more than not understanding maths. It's like the world has gone mad!

Reply 9

makesomenoise

mik1a

y = (116-21x^2)/120
= 116/120 - (21/210)x^2
dy/dx = -2(21/210)x
= -5x

Dude, she said the answer said something else, that isn't your answer.

Reply 10

IntegralAnomaly

mik1a

y = (116-21x^2)/120
= 116/120 - (21/210)x^2
dy/dx = -2(21/210)x
= -5x

errm,no.Its y=116/120 - (21x^2)/120 => dy/dx=-42x/120
were did (21/210)x^2 come from?

Reply 11

makesomenoise

IntegralAnomaly

errm,no.Its y=116/120 - (21x^2)/120 => dy/dx=-42x/120
were did (21/210)x^2 come from?

(21x^2)/120 = (21/120)(x^2*1) apparently...

Reply 12

IntegralAnomaly

XTinaA

(21x^2)/120 = (21/120)(x^2*1) apparently...

It does??!! wow u must shoe me the proof :tongue:

Reply 13

makesomenoise

IntegralAnomaly

It does??!! wow u must shoe me the proof :tongue:

So you're being sarcastic, yeah? :biggrin:

Reply 14

hitchhiker_13

Ah, the world makes sense again!

Reply 15

IntegralAnomaly

XTinaA

So you're being sarcastic, yeah? :biggrin:

erhmmm,sorry about that

Reply 16

lgs98jonee

CoraBelle

Ok, i have maths homework in for tomorrow, can anyone do differentiation? (obviously i haven't quite perfected technique yet);

i need to find dy/dx when y= (116-21x^2) divided by 120.

Anyclues?

isnt it just dy/dx=-42x/120=-7x/20????

Reply 17

IntegralAnomaly

CoraBelle

If a point on a curve is parallel to a line then it follows that the gradient of the curve at that point is the same as the gradient of the line,if that just wooshed past ur head draw it and then u'll c

Reply 18

Ally45

Quote:
--------------------------------------------------------------------------------
Originally Posted by Ally45
unfortunately not everything mik1a says goes... hes just plain wrong. that is not how you differentiate that function. this first reply was perfectly correct. look again mik1a and dazya
--------------------------------------------------------------------------------

what? please explain this to me sum1

all i was saying mate is that mik1a is wrong.... hes confused himself somewhere! if you dont understand why i've siad this, hit the books and go back to differentiation from first principles.

Reply 19

lgs98jonee

Ally45

Quote:
--------------------------------------------------------------------------------
Originally Posted by Ally45
unfortunately not everything mik1a says goes... hes just plain wrong. that is not how you differentiate that function. this first reply was perfectly correct. look again mik1a and dazya
--------------------------------------------------------------------------------

what? please explain this to me sum1
dont worry...i wasnt saying that mik1a was right or nething...just confused with every1 seemingly putting different answers to wot was surely a normal differentiation q...i put my answer further up and it seems correct
all i was saying mate is that mik1a is wrong.... hes confused himself somewhere! if you dont understand why i've siad this, hit the books and go back to differentiation from first principles.