JEE Mains · Maths · STD 12 - 3 and 4 . metrices and determinant
If the system of equations \(x-2 y+3 z=9\) \(2 x+y+z=b\) \(x-7 y+a z=24\) has infinitely many solutions, then \(a - b\) is equal to
- A \(5\)
- B \(11\)
- C \(8\)
- D \(3\)
Answer & Solution
Correct Answer
(A) \(5\)
Step-by-step Solution
Detailed explanation
\(D =\left|\begin{array}{ccc}1 & -2 & 3 \\ 2 & 1 & 1 \\ 1 & -7 & a \end{array}\right|=0 \Rightarrow a =8\) also, \(D _{1}=\left|\begin{array}{ccc}9 & -2 & 3 \\ b & 1 & 1 \\ 24 & -7 & 8\end{array}\right|=0 \Rightarrow b =3\) hence, \(a- b =8-3=5\)
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