Search All of the Math Forum:

Views expressed in these public forums are not endorsed by NCTM or The Math Forum.

Topic: Can I get any help on this?
Replies: 4   Last Post: Oct 7, 2006 12:41 AM

 Messages: [ Previous | Next ]
 lateralus Posts: 3 From: superior, WI Registered: 10/5/06
Can I get any help on this?
Posted: Oct 5, 2006 9:12 PM

ok i've been working on this for quite some time:

we all know the quadratic formula:
(-b+-?b2-4ac)/2a

and this we know will give us two answers for x

so what we know are: A,B,C ANSWER 1 AND ANSWER 2 (which we'll call A1 and A2)

(2x+6)(3x+9)=0 when you do the foil method this turns into:

6x2+36x+54=0

and we know x=-3 and x=-3 (that worked out nicely)

ok so for this equasion

A=6........A1=-3
B=36.......A2=-3
C=54

now i want to be able to change this into radical form just knowing that information. so here's what i've come up with (remember the equasion in radical form is:
(2x+6)(3x+9)
so i've given variable names to those numbers in the radical form of the equasion in order W,X,Y,Z

so in this case,

(2X+6)(3X+9)
.W..X..Y..Z

W=2
X=6
Y=3
Z=9

see what i'm saying?

ok so i've defined each variable you might have to look at this for a while to see what i'm saying remember we only know a,b,c,a1,and a2 we don't know W,X,Y,or Z.

W=A/Y....................X=C/Z
W=X/-AN..................X=W*-AN
W=(B-YX)/Z...............X=(B-ZW)

Y=Z/W....................Z=C/X
Y=Z/-AN2.................Z=Y*-AN2
Y=(B-ZW)/X...............Z=(B-YX)/W

so what i want is to define at least one variable using only the information I know (A,B,C,AN1,AN2)
so i start with (using what i know from the above info):
NOTE: A MEANS A/Z THERE IS NO UNDERLINE SORRY
..........Z

Y=A/W

Y=A/(B-YX)
........(..Z.)

Y=A/(B-YX)
.......(Y*-AN2)

Y=A/[B-Y(B-ZW)]
.......[.....(..Y.)..]
.......[....Y*-AN2.]

Y=A/{B-Y[B-((Y*-AN2)*(A/Y))]}
.......{.....[.............Y...........]}
.......{...........-AN2*Y............}

ok see how i only have one unknown variable which is Y.

my problem is i can't simplify this so Y is on one side of the = sign. can anyone help me? or do you see any problem in my math?