Question

in a square matrix the elements of a column are 2,5k+1,3 and cofactors of another column are 1-5k,2,4k-2 then k=​

Answer 1

Answer:

Here, A=∣∣∣∣521302813∣∣∣∣

First we will find minor of second row.

M21=9−16=−7

M22=15−8=7

M23=10−3=7

Now, we will find the cofactors using these minors.

A21=(−1)2+1M21=−1(−7)=7

A22=(−1)2+2M22=1(7)=7

A23=(−1)2+3M23=−1(7)=−7

Now, a21=2

a22=0

a23=1

∴Δ=a21A21+a22A22+a23A23

⇒Δ=2(7)+0(7)+1(−7)=14+0−7=7

∴Δ=7.

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