Got Homework?
Connect with other students for help. It's a free community.
Here's the question you clicked on:
 0 viewing
pleasssse helpp me !
find the value of K for which x + 4y + K = 0 is a tangent to x^2 + y^2  2x + 2y  15 = 0
 one year ago
 one year ago
pleasssse helpp me ! find the value of K for which x + 4y + K = 0 is a tangent to x^2 + y^2  2x + 2y  15 = 0
 one year ago
 one year ago

This Question is Closed

malevolence19Best ResponseYou've already chosen the best response.1
You need implicit differentiation \[2x+\frac{dy}{dx}2y2+2 \frac{dy}{dx}=0 \implies x2+\frac{dy}{dx}(y+2)=0 \implies \frac{dy}{dx}=\frac{2x}{y+2}\] \[yy_0=\left. \frac{dy}{dx} \right\_{x_0,y_0}(xx_0)\] So you need a point. Then you can find the equation then identify K
 one year ago

samnathaBest ResponseYou've already chosen the best response.0
see i can't do it that way as we have not done differentiation so it confuses me i know there is another way like you can rearrange the first equation so that x = .... and then sub it into the other one but after i do that i'm no sure what to do
 one year ago

malevolence19Best ResponseYou've already chosen the best response.1
If you just solve the first one for x: \[x=4yK \] And plug it in you get: \[(4y+K)^2+y^2+2(4y+K)+2y=0\] From this you can solve for K in terms of y. As long as you know the slope and everything is write for the original line this will give you the value which allows it to cross tangential. But the slope changes every small increment you move so I don't feel convinced that the slope (in general) can just be 1/4...
 one year ago

samnathaBest ResponseYou've already chosen the best response.0
how do i get the slope from that ?
 one year ago

samnathaBest ResponseYou've already chosen the best response.0
do i multiply out the equations so i get this \[16y ^{2} + 8yk + k ^{2} + y ^{2} + 8y + 2k + 2y  15\]
 one year ago
See more questions >>>
Your question is ready. Sign up for free to start getting answers.
spraguer
(Moderator)
5
→ View Detailed Profile
is replying to Can someone tell me what button the professor is hitting...
23
 Teamwork 19 Teammate
 Problem Solving 19 Hero
 Engagement 19 Mad Hatter
 You have blocked this person.
 ✔ You're a fan Checking fan status...
Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.