Medium INTEGER +4 / -1 PYQ · JEE Mains 2021

Let a, b, c, d in arithmetic progression with common difference $\lambda$. If $$\left| {\matrix{ {x + a - c} & {x + b} & {x + a} \cr {x - 1} & {x + c} & {x + b} \cr {x - b + d} & {x + d} & {x + c} \cr } } \right| = 2$$, then value of $\lambda$2 is equal to ________________.

Answer (integer) 1

Solution

$$\left| {\matrix{ {x + a - c} &amp; {x + b} &amp; {x + a} \cr {x - 1} &amp; {x + c} &amp; {x + b} \cr {x - b + d} &amp; {x + d} &amp; {x + c} \cr } } \right| = 2$$<br><br>${C_2} \to {C_2} - {C_3}$<br><br>$$ \Rightarrow \left| {\matrix{ {x - 2\lambda } &amp; \lambda &amp; {x + a} \cr {x - 1} &amp; \lambda &amp; {x + b} \cr {x + 2\lambda } &amp; \lambda &amp; {x + c} \cr } } \right| = 2$$<br><br>${R_2} \to {R_2} - {R_1},{R_3} \to {R_3} - {R_1}$<br><br>$$ \Rightarrow \left| {\matrix{ {x - 2\lambda } &amp; 1 &amp; {x + a} \cr {2\lambda - 1} &amp; 0 &amp; \lambda \cr {4\lambda } &amp; 0 &amp; {2\lambda } \cr } } \right| = 2$$<br><br>$\Rightarrow 1(4{\lambda ^2} - 4{\lambda ^2} + 2\lambda ) = 2$<br><br>$\Rightarrow {\lambda ^2} = 1$

About this question

Subject: Mathematics · Chapter: Matrices and Determinants · Topic: Types of Matrices and Operations

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