Practicing Success
Let $p(x)$ be a function defined on $R$ such that $p'(x)=p'(1-x)$ for all $x \in[0,1], p(0)=1$ and $p(1)=41$. Then, $\int\limits_0^1 p(x) d x$ equals |
41 42 $\sqrt{41}$ 21 |
21 |
We have, $p'(x)=p'(1-x)$ i.e., $\frac{d}{d x} p(x)=\frac{d}{d(1-x)}\{p(1-x)\}$ $\Rightarrow p(x)=-p(1-x)+C$ .....(i) Putting $x=0$ in (i), we get $p(0)=-p(1)+C \Rightarrow C=42$ ......(ii) Putting $C=42$ in (i), we get $p(x)=-p(1-x)+42$ Now, $\int\limits_0^1 p(x) d x=\int\limits_0^1 p(1-x) d x$ $\Rightarrow \int\limits_0^1 p(x)=\int\limits_0^1\{42-p(x)\} d x$ $\Rightarrow 2 \int\limits_0^1 p(x) d x=42$ $\Rightarrow \int\limits_0^1 p(x) d x=21$ |