On Tue, 01 Apr 2008 13:22:41 GMT, Elmer <nylicens@[EMAIL PROTECTED]
>
wrote:
>Philippe 92 wrote:
>> ... wrote :
>>> On Tue, 01 Apr 2008 04:19:16 GMT, Elmer <nylicens@[EMAIL PROTECTED]
>
>>> wrote:
>>>> ... wrote:
>>>>> You got a sign wrong.
>>>>>
>>>>> (-6 - y)^2 =3D 36 + 12y + y^2
>>>> Well obviously I haven't a clue how to solve 12y+y^2=3D28.
>>>>
>>>> That's why I kept thinking I was way wrong. Sheest!
>>> Does that mean everything is clear now, or is there still a problem?
>>=20
>> It seems then that elmer doesn't know how to solve
>> (-6 - y)^2 =3D 64 ...
>>=20
>> I have no idea how to *explain* z^2 =3D 64 =3D> z =3D +/- 8 ...
>>=20
>> Regards.
>
>You're absolutely right. I have no idea what I'm doing. A case of the =
blind=20
>leading the blind.
>
>d=3D10 with point A=3D(4, -6) and B=3D(-2, y)
>
>so
>
>100=3D36+(-6-y)^2
>64=3D(-6-y)^2
>
>and here is where everything goes off the rails for me. I haven't a =
clue!
It doesn't matter which of A or B you take to be (x1, y1), so solving
either of the following gets the job done.
10^2 =3D (4 + 2)^2 + (-6 - y)^2 (*)
10^2 =3D (-2 - 4)^2 + (y + 6)^2 (**)
Let's solve (*) first:
100 =3D 36 + (-6 - y)^2
(-6 - y)^2 =3D 64
At this point, the easy way to proceed is to take the square root of
both sides, so
-6 - y =3D +8 or -6 - y =3D -8
Solving for y,
-y =3D +8 + 6 -y =3D -8 + 6 =20
y =3D -14 y =3D 2
So, B =3D (-2, -14) or B =3D (-2, 2)
Now let's solve (**):
100 =3D 36 + (y + 6)^2
(y + 6)^2 =3D 64
Again, taking the square root of both sides,
y + 6 =3D +8 or y + 6 =3D -8
Solving for y,
y =3D 2 y =3D -14
so again, B =3D (-2, 2) or B =3D (-2, -14)
Now, one could also expand either of (-6 - y)^2 or (y + 6)^2
and solve the resulting equation using the quadratic formula
<http://en.wikipedia.org/wiki/Quadratic_equation>,
but the solution
method above is easier.
=46or example, using (*),
10^2 =3D (4 + 2)^2 + (-6 - y)^2=20
100 =3D 36 + 36 + 12y + y^2
28 =3D 12y + y^2
y^2 + 12y - 28 =3D 0
The quadratic formula gives the solutions y =3D 2 and y =3D -14
In your original posting, you said that this was a GED test question.
If it's a multiple choice question, then perhaps only one of
B =3D (-2, 2) or B =3D (-2, -14) is given as a possible answer.
=20
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