Question

Find the value of a and b so that the polynomial x cube minus 3 x square + a x + b is exactly divisible by x minus 21

Answer 1

Answer:

x^3 - 3x^2+ax +b

x-21=0

x=21

21^3-3(21)^2+21a+b=0

9261-1323+21a+b=0

7938+21a+b=0

21a+b=-7938

a+b= 7938/21

a+b=378