# maths - roots of equation

• Dec 7th 2009, 07:55 PM
deej813
maths - roots of equation
for what valus of k does x^2 + (k+2)x + (k+2) = 0 have equal roots??
• Dec 7th 2009, 07:58 PM
pickslides
Quote:

Originally Posted by deej813
for what valus of k does x^2 + (k+2)x + (k+2) = 0 have equal roots??

It has repeated roots at \$\displaystyle (k+2)^2-4(k+2)=0\$
• Dec 7th 2009, 08:00 PM
deej813
um ok
can you explain how?
so what values of k??
• Dec 7th 2009, 08:03 PM
TheEmptySet
Quote:

Originally Posted by deej813
um ok
can you explain how?
so what values of k??

It will have repeate roots when the discriminat is equal to zero.

The discrimiant is the \$\displaystyle b^2-4ac\$ part of the quadratic equation(the stuff under the radical)

Solve the above equation to get the "two" values for k (pun intended)
• Dec 7th 2009, 08:06 PM
deej813
so its when k is + or - 2
• Dec 8th 2009, 09:15 PM
T. Student
roots
You are correct. There will be two parabolas with one root each. Each parabola has a vertex touching the x-axis.