An expression that is equivalent to (-8a-1)-(-7a+5)

Wilma worker has a $90,000 insurance policy for which she pays $1,200 a year. to compare the cash value of the policy to investing the same amount of money at 6%, she performs the following calculations:

What are the possible rational zeros of [tex]f(x) = x^4+2x^3-3x^2-4x+18[/tex]

Whats are the trickiest steps to do when adding or subtracting rational expressions? how does knowledge of rational numbers u in adding and subtracting rational expressions?