# Math Help - Which options gives f(7-x)

1. ## Which options gives f(7-x)

I simply worked f(7-x) out and got the answer exactly described in (d). And x 19/3 and 0 ≤ x ≤ 7 seem appropriate too.

Now I wonder if there is any tricky thing in other areas. Would any fellow please take a look when you have time.

2. Originally Posted by pozat
I simply worked f(7-x) out and got the answer exactly described in (d). And x 19/3 and 0 ≤ x ≤ 7 seem appropriate too.

Now I wonder if there is any tricky thing in other areas. Would any fellow please take a look when you have time.

3. Since $f(x)= \frac{-2x^2+1}{3x-2)^2}$, $f(7- x)= \frac{-2(7-x)^2+ 1}{3(7-x)-2)^2}= \frac{-2(49- 14x+ x^2)+ 1}{21- 3x- 2)^2}$ $= \frac{-97+ 28x- 2x^2}{(19- 3x)^2}$. That's "d".