if f(x) = x^2 - 2x, find f(x+2) - f(2) / 2

Question

the answer is: x+2

but l got: x^2 - 2x - 8 = 0

which is x = 4 or x = -2

Answer 1

=[(x+2)^2 - 2(x+2)] - [(2)^2 - 2(2)]/2
=x^2+4x+4 - 2x-4 - (4-4)/2
=x^2+2x - 0
=x(x+2)
= 0 or -2

I have the x+2 part of your "correct answer", but I also got the "x" in there. That's the answer I came up with, if you don't understand how I arrive my answer, let me know.

Answer 2

wait, i mistyped. it should be:

if f(x) = x^2 - 2x, find f(x+2) - f(2) / x

divided by x, not 2.

sorry...

Answer 3

Hmm... that should be the same answer because f(2) = 0 and 0 divide by any number is 0 and "x" cannot be zero.

Answer 4

well i redid it and i got this:

= x^2 + 4x + 4 - 2x - 4 - 2^2 - 4 / 2
= x^2 + 2x / x

divide the x and i get "x+2"

is it correct??

Answer 5

Where is the /x comes from on your x^2+2x/x... you were /2 up there on the above step... and even if the problem is f(2)/x... your f(2) = 0, that mean you get 0/x which equals 0, thus leaving you only x^2+2x on the left side, which equals x(x+2).

Basically, I disagree with what you did up there because you can't just go from:

x^2 + 2x - 0/x to (x^2 + 2x)/x