\(f(x) = x^2-kx+18\). One root is twice the other. Find the roots.
I got 3 and 6 from this since Vieta's formula says that the product of the roots must be 18 and 3*2 = 6. Did I do it correctly?
+9479 Let a and b be the roots. Then we can make these two equations:
ab = 18 and a = 2b
Substituting 2b in for a into the first equation, we get:
(2b)b = 18
2b2 = 18
b2 = 9
b = ± 3
Which means.....
a = 2 * (± 3)
a = ± 6
So 3 and 6 is one possible solution, and the other possible solution is -3 and -6 
+9479 Let a and b be the roots. Then we can make these two equations:
ab = 18 and a = 2b
Substituting 2b in for a into the first equation, we get:
(2b)b = 18
2b2 = 18
b2 = 9
b = ± 3
Which means.....
a = 2 * (± 3)
a = ± 6
So 3 and 6 is one possible solution, and the other possible solution is -3 and -6
