Finding equation of both lines

  • Thread starter Meeker
  • Start date
  • #1
Meeker
5
0

Homework Statement



Determine the equation of both lines that are tangent to the graph of y=x^2 +4 and pass through the point (1,-2)

Homework Equations





The Attempt at a Solution



The derivative/slope of the tangent is 2x. But I'm not too sure what to do with this.
 

Answers and Replies

  • #2
Dick
Science Advisor
Homework Helper
26,263
620
Ok so let (x,y) be a point on your curve. That makes it (x,x^2+4), right? Now find the slope of the line between that point and (1,-2). That slope should be your 2x, also right? Now solve for x.
 
  • #3
Meeker
5
0
Ok so let (x,y) be a point on your curve. That makes it (x,x^2+4), right? Now find the slope of the line between that point and (1,-2). That slope should be your 2x, also right? Now solve for x.

Alright. Once I find x, what do I do with it?.

Btw, the slope for that line is (x-1)/(x^2+6) rite?
 
  • #4
Dick
Science Advisor
Homework Helper
26,263
620
Alright. Once I find x, what do I do with it?.

Btw, the slope for that line is (x-1)/(x^2+6) rite?

Slope is delta(y)/delta(x), isn't it? Once you find values for x, each one gives you a point on the curve that also goes through (1,-2). Use the points to find the line equations.
 

Suggested for: Finding equation of both lines

Replies
8
Views
218
  • Last Post
Replies
2
Views
319
  • Last Post
Replies
1
Views
312
Replies
4
Views
354
Replies
3
Views
501
Replies
23
Views
381
  • Last Post
Replies
7
Views
292
Replies
20
Views
707
Replies
12
Views
694
Top