Question

find a and b if (x+1) and (x-2) are factor of x3 +ax2+2x+b.​

Answer 1

p(x)=x3+ax2+2x+b

p(-1)= -1+1a+-2+b

= -3+a+b

-3+a+b=0

b=3-a

p(2)=8+4a+4+b

=12+4a+b

12+4a+3-a

15+3a=0

3a=-15

a=-5

b=3--5=8