If f(x) is a polynomial satisfying $f(x) = x^3+x^2 f'(1)+x f''(2)+f'''(3)$ for all $x \in R$. Then,
Answer & explanation
Correct answer: option 4
We have,
$f(x)=x^3+x^2 f^{\prime}(1)+x f^{\prime \prime}(2)+f^{\prime \prime \prime}(3)$ ....(i)
$\Rightarrow f^{\prime}(x)=3 x^2+2 x f^{\prime}(1)+f^{\prime \prime}(2)$ ....(ii)
$\Rightarrow f^{\prime \prime}(x)=6 x+2 f^{\prime}(1)$ ....(iii)
$\Rightarrow f^{\prime \prime \prime}(x)=6$ ....(iv)
Putting $x=1,2,3$ in (ii), (iii), and (iv) respectively, we get
$f^{\prime}(1)=3+2 f^{\prime}(1)+f^{\prime \prime}(2)$
$f^{\prime \prime}(2)=12+2 f^{\prime}(1), f^{\prime \prime \prime}(3)=6$
Solving these equations, we get
$f^{\prime}(1)=-5, f^{\prime \prime}(2)=2$ and $f^{\prime \prime \prime}(3)=6$
∴ $f(x)=x^3-5 x^2+2 x+6$
$\Rightarrow f(0)=6, f(1)=4, f(2)=8-20+4+6=-2$ and, f(3) = -6
Clearly, these values satisfy options (1), (2) and (3).