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# Core 3 watch

1. A curve has the equation y = (3x − 5)^3 .

part i - Find an equation for the tangent to the curve at the point P (2, 1).

The tangent to the curve at the point Q is parallel to the tangent at P.
part ii - Find the coordinates of Q.

The equation of the tangent to the curve at point P is y = 9x-17.

How do i find the co-ordinates of Q?
2. Because the two tangents are parallel, they have the same gradient.

Does this help?
3. i understand the bit about the equations having the same gradient but i'm not sure which equation i should substitute 9 into and solve?
4. (Original post by Chelsea12345)
i understand the bit about the equations having the same gradient but i'm not sure which equation i should substitute 9 into and solve?
You dont sub it into anything.

You’re looking for another point with gradient 9, so set dy/dx=9
5. (Original post by RDKGames)
You dont sub it into anything.

You’re looking for another point with gradient 9, so set dy/dx=9
thankyou
6. (Original post by Chelsea12345)
i understand the bit about the equations having the same gradient but i'm not sure which equation i should substitute 9 into and solve?
Show me your working for finding the equation of the tangent at P.
7. (Original post by RDKGames)
You dont sub it into anything.

You’re looking for another point with gradient 9, so set dy/dx=9
jumped to the conclusion there a bit . I thought we wernt suppose to give answers out
jumped to the conclusion there a bit . I thought we wernt suppose to give answers out
Yeah don’t do the question for em, just tell em how to start it.

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Updated: February 16, 2018
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