1.

Evaluate \(\begin{vmatrix}X^2 -X +1& X-1 \\[0.3em]X+1& X+1 \\[0.3em]\end{vmatrix}\)

Answer»

Theorem: This evaluation can be done in two different ways either by taking out the common things and then calculating the determinants or simply take determinant. 

I will prefer first method because with that chances of silly mistakes reduces. 

Take out x+1 from second row.

\(\begin{vmatrix} X^2 -X +1& X-1 \\[0.3em] X+1& X+1 \\[0.3em] \end{vmatrix} \)

⇒(x+1) × (x2-x+1-(x-1)) 

⇒ (x+1) × (x2-2x+2) 

⇒ x3-2x2+2x+x2-2x+2 

⇒ x3-x2+2 .



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