JEE Advanced 2009Paper 2
- Exam
- JEE Advanced
- Year
- 2009
- Paper
- Paper 2
- Subject
- Mathematics
- Chapter
- Application of Derivatives
JEE Advanced 2009 · Paper 2 · Mathematics · Application of Derivatives
Let p(x) be a polynomial of degree 4 having extremum at x=1,2 and _...
Let be a polynomial of degree 4 having extremum at and . Then, the value of is
Correct answer
0
Step-by-step solution
Let
\Rightarrow \quad p^{\prime}(x)=4 a x^3+3 b x^2+2 c x+d
\therefore \quad p^{\prime}(1)=4 a+3 b+2 c+d=0
and $p^{\prime}(2)=32 a+12 b+4 c+d=0$
Since, $\lim _{x \rightarrow 0}\left(1+\frac{p(x)}{x^2}\right)=2 \quad$ [given]
$ \lim _{x \rightarrow 0}$ $\frac{a x^4+b x^3+(c+1) x^2+d x+e}{x^2}=$2
$\begin{array}{rlrl}
\Rightarrow & & x+1=2, d & =0, e=0 \\
\Rightarrow & c & =1
\end{array}$
From Eqs. (i) and (ii)
$\begin{array}{rlrl}
& & 4 a+3 b=-2 & \text{ and } 32 a+12 b=-4 \\
\Rightarrow & & a=\frac{1}{4} \text{ and } b=-1 \\
\therefore & & p(x)=\frac{x^4}{4}-x^3+x^2 \\
\Rightarrow & & p(2)=\frac{16}{4}-8+4
\end{array}$