Find the equation of the line tangent to y^2=-16x and parallel to x+y=1.

Please help me with this or just give me an idea on how to answer this problem... Thanks!

Printable View

- Feb 22nd 2010, 10:27 PMlanceParabola - find the equation
Find the equation of the line tangent to y^2=-16x and parallel to x+y=1.

Please help me with this or just give me an idea on how to answer this problem... Thanks! - Feb 22nd 2010, 10:44 PMProve It
If the line is parallel to , then its gradient is . (Why?)

You want the equation of the tangent that has the same gradient.

So

.

So when the gradient is ...

.

When we have

.

So we have the gradient and a coordinate that lies on the tangent.

Put this information into , solve for the unknown , and then you will have the equation of the tangent.