Find the sum of the coefficients in the polynomial 3(x^{10} - x^7 + 2x^3 - 6x + 7) + 4(x^3 - 2x^2 - 6) when it is simplified.
The sum of the coefficients of $f(x)$ is $f(1)$. So put $x=1$ up there and see what you get.
+600 
