1. You just need to add up the x^3 terms, which is just x^3+5x^3 = 6x^3, which means the answer is 6.
2. Since both of the polynomials are of degree 4, the largest possible value of the degree of f(x)+a*g(x) is still 4, since multiplying a polynomial by a constant doesn't change its degree.
3. To find the smallest possible degree, try to cancel out the x^4 term. To do that, set b = -1/2. That will make the x^4 term of g(x) equal to -1, which cancels out with the x^4 term of f(x), but notice that the x^2 terms also cancel out. That means the smallest possible degree is 1.
4. since both of the polynomials are of degree 4, the degree of f(x)*g(x) is just 4+4=8.
5. very similar to question 2, the answer is 11.
6. hint: this is the same question as solving this equation:
28-5+2t=0