. What is the H.C.F. of
What is the H.C.F. of x3 – x2 – 4x – 6 and x2 – 2x – 3 ?
A. x + 1
B. x – 1
C. x + 3
D. x – 3
Best Answer
Answer ||| D
Solution |||
Given: x3 – x2 – 4x – 6 and x2 – 2x – 3
To Find: HCF
We have, x3 – x2 – 4x – 6 and x2 – 2x – 3
x2 – 2x – 3
⇒ x2 – 3x + x – 3
⇒ x(x – 3) + 1(x – 3)
⇒ (x + 1)(x – 3) … (i)
Now for, x3 – x2 – 4x – 6
⇒ x3 + 2x2 – 3x2 + 2x – 6x – 6
⇒ x3 + 2x2 + 2x – 3x2 – 6x – 6
⇒ x (x2 + 2x + 2) -3 (x2 + 2x + 2)
⇒ (x – 3) (x2 + 2x + 2) … (ii)
For, x2 + 2x + 2 , D=-4<0 (No further factorization is possible)
Clearly from eqn. (i) and eqn. (ii)
HCF = (x – 3)
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