difference between the polynomials I have a homework assignment that I do not know how to solve. I don't understand how to calculate $f(x)$ in this assignment.
$f(t)$ is the difference between the polynomials $2t^3-7t^2-4$ and $t^2-7t-3$.
Calculate $f(3)$. 
What should I do to calculate $f(t)$?
Thanks!

This might be a tad too complex for the OP, so I suggest you read this answer lightly.
Let $F$ be a field, and let $F[x_i]$ be the vector space of polynomials of $i$ variables with coefficients in $F$. This is a vector space, and hence, for two polynomials $P(x_i),Q(x_i)\in F[x_i]$, there exists a $-Q(x_i)$ satisfying $Q(x_i)+(-Q(x_i))=0$, where $0$ is the zero polynomial. Then, the difference $\alpha(x_i)$ between the two polynomials  is given by $\alpha(x_i)=P(x_i)+(-Q(x_i))$. Your scenario is the case $i=1$ and $F=\mathbf{R}$, the real numbers.
