Without actual division, prove that 2x4 – 5x3 + 2x2 – x + 2 is divisible by x2 – 3x + 2. [Hint: Factorize x2–3x + 2]
First of all, factorize x2 – 3x + 2
We get
x2 – 2x-3x + 2
= x(x-2)-1(x-2)
= (x-2)(x-1)
According to remainder theorem when p(x) is divided by (x+a) then the remainder is p(-a) .
So if p(x) is divide by x2 – 3x + 2 then p(2) and p(1) must be zero
p(2)=2(2)4 -5(2)3 +2(2)2 -2+2
=32-40+8
=0
p(1)=2(1)4 -5(1)3 +2(1)2 -1+2
=2-5+2-1+2
=6-6
=0
Hence both p(1) and p(2) are zero therefore p(x) is divisible by x2 – 3x + 2
Hence proved.