how is the following equation solved and deduced

Question

i have a simple limits problem . i cannot understand how this equation is solved i mean how does f(3+h) changes to f(3+h-1)^2 ..

Answer 1

$f(3+h)$ does not change to $f(3+h-1)^2$; it changed to $(3+h-1)^2$. What has happened is the value $3+h$ was plugged into the function $f$. This means that the function $f$ must be $f(x)=(x-1)^2$ so that $f(3+h)=(3+h-1)^2$ and $f(3)=(3-1)^2$.