1.

If the system of equation 2x + 5y + 8z = 0, x + 4y + 7z = 0, 6x + 9y – αz = 0 has a non trivial solution then what is the value of α?(a) -12(b) 0(c) 12(d) 2This question was addressed to me in an online quiz.This intriguing question comes from Application of Determinants topic in section Determinants of Mathematics – Class 12

Answer»

Right choice is (c) 12

To explain I would say: Here, in L.H.S we have,

\(\begin{vmatrix}2 & 5 & 8 \\1 & 4 & 7 \\6 & 4 & \alpha \end {vmatrix}\)

So, for trivial ROOTS the above VALUE is = 0

=>\(\begin{vmatrix}2 & 5 & 8 \\1 & 4 & 7 \\6 & 4 & \alpha \end {vmatrix}\) = 0

SOLVING it further we get α = 12



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