Could anyone help me with this. I know its easy but, I completely forgot everything about math last year. (grade 11 now)

Practice Factoring Trinomials.

determine two values of c so that each expression can be factored.

a) x^2 + 4x + c

b) x^2 - 9x + c

and

Determine expressions to represent the dimensions of this rectangular prism.

Volume is x^3 + 5x^2 + 6x.

please explain ? thanks !