Ineed with geometry lol most of the questions i will be asking is about geometry so plz someone

Given that (x-3) is a factor of f(x)=x^3+ax^2-x-6, find a and hence the number of real roots or the equation f(x)=0

Iwill make brain if you me correctly fill this out needs due today pls and send it back to me (click the link and you will get it)

Two planes leave an airport at the same time, one flying east, the other flying west. the eastbound plane travels 20 mph slower. they are 1600 mi apart after 2 hr. find the speed of each plane.