Question
Let f(x) = (x - a)2 + (x - b)2 + (x - c)2. Then, f(x) has a minimum at x = 
  1. $\frac{\text{a}+\text{b}+\text{c}}{3}$
  2. $\sqrt[3]{\text{a}\text{b}\text{c}}$
  3. $\frac{3}{\frac{1}{\text{a}}+\frac{1}{\text{b}}+\frac{1}{\text{c}}}$
  4. None of these.

Answer

  1. $\frac{\text{a}+\text{b}+\text{c}}{3}$

Solution:

f(x) = (x - a)2 + (x - b)2 + (x - c)2

⇒ 2(x - a) + 2(x - b) + 2(x - c)

to find minima or maxima f'(x) = 0

2(x - a) + 2(x - b)2 + 2(x - c) = 0

$\Rightarrow \text{x}=\frac{\text{a}+\text{b}+\text{c}}{3}$
f''(x) = 6 > 0

function has minima at $\text{x}=\frac{\text{a}+\text{b}+\text{c}}{3}$.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Similar questions

If $\sin y + {e^{ - x\,\cos y}} = e,$ then ${{dy} \over {dx}}$ at $(1,\pi )$ is
If $y={{\cos }^{-1}}\cos (|x|-f(x)),$  where

$f(x)\left\{ \begin{gathered}    = 1\,,\,{\text{if}}\,\,\,x > 0 \hfill \\    =  - 1\,,\,{\text{if}}\,\,\,x < 0 \hfill \\    = 0\,,\,{\text{if}}\,\,\,x = 0 \hfill \\  \end{gathered}  \right.$ then ${\left. {\frac{{dy}}{{dx}}} \right|_{x = \frac{{5\pi }}{4}}}$ is

The matrix $A = \left[ {\begin{array}{*{20}{c}}1&{ - 3}&{ - 4}\\{ - 1}&{\,\,\,3}&{\,\,4}\\1&{ - 3}&{ - 4}\end{array}} \right]$ is nilpotent of index
If $\mathrm{U}_{\mathrm{n}}=\left(1+\frac{1}{\mathrm{n}^{2}}\right)\left(1+\frac{2^{2}}{\mathrm{n}^{2}}\right)^{2} \ldots\left(1+\frac{\mathrm{n}^{2}}{\mathrm{n}^{2}}\right)^{\mathrm{n}}$, then $\lim _{n \rightarrow \infty}\left(U_{n}\right)^{\frac{-4}{n^{2}}}$ is equal to :
If $\text{y}^\frac{1}{\text{n}}+\text{y}-^\frac{1}{\text{n}}=2\text{x}$ then find $(\text{x}^2-1)\text{y}_2+\text{xy}_1=$ 
  1. -n2y
  2. n2y
  3. 0
  4. None of these.
If $ 5$  is one root of the equation $\left| {\,\begin{array}{*{20}{c}}x&3&7\\2&x&{ - 2}\\7&8&x\end{array}\,} \right| = 0$, then other two roots of the equation are
The range of $a \in R$ for which the function $ f(x)=(4 a-3)\left(x+\log _{e} 5\right)+2(a-7) \cot \left(\frac{x}{2}\right) \sin ^{2}\left(\frac{x}{2}\right)$ $x \neq 2 n \pi, n \in N ,$ has critical points, is
Let $A =$ $\left[ {\begin{array}{*{20}{c}}{x + \lambda }&x&x\\x&{x + \lambda}&x\\x&x&{x + \lambda }\end{array}} \right]$ , then $A^{-1}$ exists if
Let $0 < P(A) < 1$, $0 < P(B) < 1$ and $P(A \cup B) = $ $P(A) + P(B) - P(A)\,P(B).$ Then
Subtraction of integers is:
  1. Commutative but no associative.
  2. Commutative and associative.
  3. Associative but not commutative.
  4. Neither commutative nor associative.