Printable View
I've been stuck on this problem for a while, after starting C1 AS level maths a few weeks ago. Here is the question:
Curve C => y = ax³ - x² + x - 5, a is some constant.
Point P => (-1/2, y)
Tangent to C at P is parallel to y = (7x - 1)/2
Find a.
Any help will be appreciated, thanks.
Parellel to y = (7/2)x - 1/2 means the slope of the tangent (at x = -1/2) is 7/2Quote:
Originally Posted by b150
So if f(x) = ax^3 -x^2 + x - 5, then f ' (-1/2) = ...
Can you take it from here?
The tangent of C isQuote:
Originally Posted by b150
and since parallel lines have the same gradient
 = \dfrac{7}{2})
Solve for a
edit: too slow
This looks like a calculus question.
Do you know how to find the derivative of this cubic function?
Do you know what a derivative tells about a function?
...but much better looking!Quote:
Originally Posted by e^(i*pi)
haha I realised how to do it like 5 minutes after I posted :P Thanks anyway.
I don't see how you can say that e^(i*pi) is much better looking ! He doesn't even show a picture of himself.Quote:
Originally Posted by TheChaz
... Oh! You mean his post was much better looking? Yes, it does look good -- LaTeX does that.