Question

If f(x+1)=2x^(2)+x+a-1
f(3)=?
a=?

Answer 1

$f(x+1)=2x^2+x+a-1$

$f(3)$ will be when $x=2$

$f(3)=2\times2^2+2+a-1=9+a$

$a$ can be any value, since we don't have more information