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Home  >>  CBSE XII  >>  Math  >>  Relations and Functions
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Let $f:R \rightarrow R$ be defined by $ f(x)=\left \{ \begin{array}{1 1} 2x:x>3\\x^2:1<1x\leq 3\\ 3x:x\leq1\end{array} \right.$ $Then\;f(-1)+f(2)+f(4)\;is$

\begin{array}{1 1}(A)\;9 & (B)\;14\\(C)\;5 & (D)\;none\;of\;these\end{array}

Can you answer this question?
 
 

1 Answer

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Toolbox:
  • For the given function
  • $f(x)= \left\{ \begin{array}{1 1} 2x & \quad ;x > 3 \\ x^2 & \quad ;1 < x \leq 3 \\3x & \quad ;x \leq 1 \end{array} \right. $
  • for $f(-1) \qquad f(x)=3x \qquad -1 \leq 1$
  • for $f(2) \qquad f(x)=x^2 \qquad 1 < 2 \leq 3$
  • for $f(4) \qquad f(x)=2x \qquad x > 3$
$f(x)= \left\{ \begin{array}{1 1} 2x & \quad ;x > 3 \\ x^2 & \quad ;1 < x \leq 3 \\3x & \quad ;x \leq 1 \end{array} \right. $
 
$f(-1)+f(2)+f(4)$
 
$=3(-1)+2^2+ 2 \times 4$
 
$=-3+4+8$
 
$=9$
 
'A' option is correct

 

answered Mar 5, 2013 by meena.p
 

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