SOLUTION: I'm just having trouble setting up this equation. Find all values of b so that the straight line 3x-y=b touches the circle x^2+y^2=25 at only one point. So I set it up as a

Question 78466This question is from textbook College Algebra
: I'm just having trouble setting up this equation.
Find all values of b so that the straight line 3x-y=b touches the circle x^2+y^2=25 at only one point.
So I set it up as a system of equations and simplified the linear equation so I could use substitution:
y=3x-b
x^2+y^2=25
Then I tried to substitute {3x-b} for y in the circle equation:
x^2+(9x^2-6xb+b^2)=25
I was stuck as to where to go from here. Mainly, how do I find b?
This question is from textbook College Algebra

Answer by renevencer22(21) (Show Source): You can put this solution on YOUR website!
please look at the following URL:
http://renevencer18.50megs.com/mathprob/tangencyconic1.jpg
http://renevencer18.50megs.com/mathprob/tangencyconic2.jpg
I hope the solutions are there.
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