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# tangents and differentiation c1 watch

1. The tangent at point P on the curve y= (3x-5)(x+2) is parallel to the line y = 7x+1. Find the co-ordinates of point P.

I've differentiated the first equation to get 6x+1 and made this equal to 7, then solved to find x, which is 1. Now what?
2. (Original post by gomc)
The tangent at point P on the curve y= (3x-5)(x+2) is parallel to the line y = 7x+1. Find the co-ordinates of point P.

I've differentiated the first equation to get 6x+1 and made this equal to 7, then solved to find x, which is 1. Now what?
assuming your working are correct put x=1 into the equation of the curve to get the corresponding y coodinate
3. (Original post by gomc)
The tangent at point P on the curve y= (3x-5)(x+2) is parallel to the line y = 7x+1. Find the co-ordinates of point P.

I've differentiated the first equation to get 6x+1 and made this equal to 7, then solved to find x, which is 1. Now what?
So you have , what value does your curve take when you sub into it?

4. (Original post by TeeEm)
assuming your working are correct put x=1 into the equation of the curve to get the corresponding y coodinate
Beaten again.
5. (Original post by gomc)
The tangent at point P on the curve y= (3x-5)(x+2) is parallel to the line y = 7x+1. Find the co-ordinates of point P.

I've differentiated the first equation to get 6x+1 and made this equal to 7, then solved to find x, which is 1. Now what?

The gradient of the tangent to the curve at point P is equal to the gradient of the line y = 7x + 1.

You need to put the differential of the first equation equal to the gradient of the line and solve for x.
Does it make sense why you would do that?
Never mind, I can't read, apparently. Ignore me! :P
6. but when i plot the two graphs they dont cross at (1,-6)?? no where near
7. (Original post by Zacken)
Beaten again.
is all this LaTeX typing ...
8. (Original post by gomc)
but when i plot the two graphs they dont cross at (1,-6)?? no where near
Because the line is parallel to the tangent at , it's not the actual tangent and hence will not cross the line.

The tangent to the curve at is given by .
9. (Original post by Zacken)
Because the line is parallel to the tangent at , it's not the actual tangent and hence will not cross the line.

The tangent to the curve at is given by .
god how did i miss that im so tired lol thanks though
10. (Original post by gomc)
god how did i miss that im so tired lol thanks though
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Updated: October 23, 2015
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