functions and quadratic equations

[denian]

if x=2 is a root of ax^2 - bx -x = 0, state the relationship connecting a,b, c and show that x=2 is also a root of
bx^2 + cx - 8a = 0.

the answer for the first part of the question is
4a - 2b - c = 0.

i need to know how to prove for the second part.

[Guybrush Threepwood]

bx2 + cx - 8a = 0 ???
I can get bx2 + 2cx - 8a = 0 .....

[denian]

i do not type wrongly. however, can u tell me how you get that?

[Guybrush Threepwood]

Originally posted by denian
i do not type wrongly

if x=2 is a root of ax^2 - bx -x = 0, state the relationship connecting a,b, c

am I mean or what [8)]

anyway, I just multiplied your last result with -2. and yes, you were right, I was mistaken in the last post. It is
bx2 + cx - 8a = 0

I just get out of a meeting [g)]

[denian]

i still cant get what you mean.

[Guybrush Threepwood]

Originally posted by denian
the answer for the first part of the question is
4a - 2b - c = 0.


if you multiply by -2 you get
-8a + 4b + 2c = 0


show that x=2 is also a root of
bx^2 + cx - 8a = 0.


now did you get it?

[denian]

tq. now i know what you mean.