Because this is a fifth degree polynomial, it's an odd function. Odd functions have one tail go up and the other down. Because the leading coefficient is a negative number, 3 to be exact, the left one goes up and the right goes down.
0.04, just divide 4 by 100
Probably true
you can test it too
He will weigh 198 lbs. you add 3 lbs to his original weight for each year.