Question

Find f(k - 1) when f(x) = 5x^2+ 4x – 5.

Answer 1

Plug in $k-1$ to each $x$ in the function.

$f(k-1)=5(k-1)^2+4(k-1)-5$

$f(k-1)=5(k^2-2k+1)+4k-4-5$

$f(k-1)=5k^2-10k+5+4k-4-5$

$f(k-1)=5k^2-6k-4$

Hope this helps.

頑張って!