Please Help the Talnesssssss yet again again again

Former Member

Stuck with math, and it went so well until now

I get told that the line with the equation 4y=4x + a is the tangent to the equation squareroot of x. How do I find a?

Anyone???

P.S. From now I will drag this thread up everytime I need help. I will try not to annoy you all so much though. But I can't help it. Have posponed this for too long

EDIT: It's all about differentating and such piss and paperdom.

Former Member

Isn't "a" where the tangent touches the curve?

I haven't done maths since I took Add Maths AO Level 2 years ago. So I may be wrong. Hope someone can tell you!

Former Member

b is where the line touches the y-curve. a is the incline of x.

But in this case I wouldn't know

Former Member

I could help you if i had a diagram but i cant picture it!

Former Member

HELP NEEDED ASAP!
Need to make a graph on excel which goes a*x^b (which is a kinf of double exponential), and I have no clue of how to.

Anybody knows?

Former Member

Havent got a clue tbh Tal-Anna. But, I do like your av.

Former Member

Thank yew Lisa-Marieness

Former Member

Originally posted by Jacqueline the Ripper
Thank yew Lisa-Marieness

Tis your eye too, oui?

Former Member

here goes.....

you have 4y=4x+a which is the same as y=x+(a/4), and root x which is x^0.5

this is a standard straight line of form y=mx+c, m being the gradient which in this case is 1, and c being a constant (the y-axis intercept)

where the two curves intercept tangentially their gradients must be the same

You know the gradient of 4y=4x+a is 1, hence the gradient of y=x^0.5 must be 1 at that point

By differentiating: dy/dx x^0.5 = 0.5x^-0.5

now you have to set this equal to 1, so 0.5x^-0.5 = 1

from this you can calculate that x=0.25

From y=x^0.5 you can calculate that when x=0.25 y=0.5. You now have an x and a y co-ordinate for the point where the curves meet. By plugging these back into the eqn y=x+(a/4),

0.5=0.25+(a/4)

and from this you can calculate the value of 'a' as being 1

hope that helps!

Former Member

he he I tried doing that, but I got stuck. damnations.
It's been one hell of a weekend...

Bopz

(Can't wait to start the modelling lecture at 9 am tommorow! :eek: )

Former Member

Originally posted by *Lisa*
Tis your eye too, oui?

Oui oui, mon cherie.