Can anyone help me with these three sums!!

(x+5)(x-4)(x-a)=xto the cube+bx to be square-23x+c=0

Find the values of a,b, and c

x to be squard+6x-k is afactor of x to be cube+kx to be squared-x-k!!Find the value of k!!Hence solve the following equation x to cubed+kx to be squared-x-k=0

(x to be squared+ax+b) is a factor of 2x to cube+ax to be squared+13x+b

Find the values of a and b

Thanks alot!!