F.4數學3題~~help me please.....

a即係alpha b即係beta

1.
If a and b are the roots of the equation 10x^2-4x-5=0, find the value of the following.
(a+1/b)(b+1/a)

2.
Let c be a constant. If -2 is a root of the equation 5x^2-4x+c=0, find the other root and the value of c.

3.
If a and b are the roots of the equation x^2+9x+4=0, find the value of the following.
a^3+b^3