Prove the following

Question:

Let $a-2 b+c=1$

If $f(x)=\left|\begin{array}{lll}x+a & x+2 & x+1 \\ x+b & x+3 & x+2 \\ x+c & x+4 & x+3\end{array}\right|$, then :

 

  1. (1) $f(-50)=501$

  2. (2) $f(-50)=-1$

  3. (3) $f(50)=-501$

  4. (4) $f(50)=1$


Correct Option: , 4

Solution:

If $f(x)=\left|\begin{array}{lll}x+a & x+2 & x+1 \\ x+b & x+3 & x+2 \\ x+c & x+4 & x+3\end{array}\right|$

$R_{1}=R_{1}+R_{3}-2 R_{2}$

$\Rightarrow \quad f(x)=\left|\begin{array}{ccc}1 & 0 & 0 \\ x+b & x+3 & x+2 \\ x+c & x+4 & x+3\end{array}\right|$

$\Rightarrow f(x)=1 \Rightarrow f(50)=1$

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