d2jsp
Log InRegister
d2jsp Forums > Off-Topic > General Chat > Homework Help > Calc 1 Help
Add Reply New Topic New Poll
Member
Posts: 7,236
Joined: Jan 31 2009
Gold: 0.30
Feb 27 2014 03:02pm
Find all points of the graph f(x) = x^2 +4 that have a tangent that passes through (0,0)
Member
Posts: 724
Joined: Jan 19 2010
Gold: 9,788.18
Feb 27 2014 03:11pm
NVM, thought about it upside down

This post was edited by allthelivelongday on Feb 27 2014 03:12pm
Member
Posts: 1,241
Joined: Jun 25 2011
Gold: Locked
Feb 27 2014 03:44pm
Here's how id do it:
-the equation of the tangent for x=a is y=f'(a)(x-a)+f(a)
-the tangent passes through (0,0) iff x=0 and y=0, thus it passes through (0,0) iff 0=-af'(a)+f(a)
-thus, the answers are the solutions to the equation -a^2+4=0 , so (2,8) and (-2,8) are the solutions.

This post was edited by m0hawk on Feb 27 2014 03:55pm
Member
Posts: 7,236
Joined: Jan 31 2009
Gold: 0.30
Feb 27 2014 04:49pm
Quote (m0hawk @ Feb 27 2014 07:14pm)
Here's how id do it:
-the equation of the tangent for x=a is y=f'(a)(x-a)+f(a)
-the tangent passes through (0,0) iff x=0 and y=0, thus it passes through (0,0) iff 0=-af'(a)+f(a)
-thus, the answers are the solutions to the equation -a^2+4=0 , so (2,8) and (-2,8) are the solutions.


I'm lost even at this lol,
Member
Posts: 7,721
Joined: Oct 11 2008
Gold: 304.00
Feb 27 2014 04:59pm
Quote (Illumini @ Feb 27 2014 04:49pm)
I'm lost even at this lol,


he's skipping some steps but that is 6/7th grade algebra 1, y=mx+b


so, just take your derivative to find slope then apply 6/7th grade algebra 1 equations, y=mx+b

Go Back To Homework Help Topic List
Add Reply New Topic New Poll