Monday, March 31, 2014

What are the values of parameter m if the vertex of parabola y = x^2-2(m-1)*x+m-1 is on the first bisector line?

Firts, we'll determine the coordinates of the vertex of
the parabola.


V(-b/2a ;
-delta/4a)


deta = b^2 -
4ac


a,b,c, are the coefficients of the
quadratic.


a = 1 , b = -2(m-1) , c =
m-1


xV = 2(m-1)/2


xV = 2m -
2


delta = 4(m-1)^2 -
4(m-1)


delta =
4(m-1)(m-1-1)


delta =
4(m-1)(m-2)


yV =
-4(m-1)(m-2)/4


yV =
-(m-1)(m-2)


The coordinates of the vertex are: V(2m - 2
;  -(m-1)(m-2)).


We'll impose the constraint of enumciation
that the vertex has to be located on the bisectrix of the first
quadrant.


yV = xV


2m - 2 =
-(m-1)(m-2)


2(m-1) =
-(m-1)(m-2)


We'll add
(m-1)(m-2):


2(m-1) + (m-1)(m-2) =
0


We'll factorize by
(m-1):


(m-1)(2 +m - 2) =
0


m(m-1) = 0


m1 =
0


m-1 = 0


m2 =
1


The values of m for the vertex of the
parabola to be on the bisector of the 1st quadrant are: {0 ;
1}.

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