Practicing Success
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, |
$f(0)+f(2)=f(1)$ $f(0)+f(3)=0$ $f(1)+f(3)=f(2)$ all the above |
all the above |
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). |