MedVision ad

Polynomials (1 Viewer)

K

khorne

Guest
Hey

I have a question:

x^3 +mx^2 +15x - 7 = 0 and has two equal roots, find m:

Firstly, I constructed the roots equations:

2a + b = -m

a^2 + 2ab = 15

a^2b = 7

And then, (with help from Mr Squidge) differentiated, as P(x)=P'(x) = 0 (on a double root)...and got the additional equation of 3x^2 + 2mx + 15 =0

However, no amount of fiddling with these equations gives an answer for any root, let alone m...So can anyone suggest anything?

I know it can be done by (x-a)(x-a)(x-b) and from inspection, b = 7, a = 1, but this was under the polynomial roots heading, so I'm pretty sure I have to use roots.

Thanks
 

a-almaz

New Member
Joined
Mar 9, 2009
Messages
1
Gender
Female
HSC
2010
Yes, t'would be good to know XD

I've been trying for a while too
 

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top