Jump to content

Equation for intersecting tangent lines


dcowboys107

Recommended Posts

Write equations for the two straight lines that pass through the poing (2,5) and are tangent to the parabola y=4x-x^2.

 

I drew the figure and the lines. I fought the slope for the tangent lines (2 and -2) and eventually the equations y=-2x+9 and y=2x+1

 

When I plugged the three equations into my calcuator to see if I was right it seems that I was off on y=-2x+9, that it doesn't reach 5 when x is two but at 4. The second one seems right.

 

Am I right and the calcultar be wrong? Thanks.

Link to comment
Share on other sites

It looks like it, and when I checked it by hand and calculator it seemed to work. So I am assuming you must have just entered something improperly into your calculator. (Ergo why I asked you to check it manually.)

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.