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If the system of equations \(\begin{aligned}& 2 x+3 y-z=5 \\& x+\alpha y+3 z=-4 \\& 3 x-y+\beta z=7\end{alig…

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If the system of equations

\(\begin{aligned}& 2 x+3 y-z=5 \\& x+\alpha y+3 z=-4 \\& 3 x-y+\beta z=7\end{aligned}\)

has infinitely many solutions, then \(13 \alpha \beta\) is equal to

[JEE Main 2024, 1 Feb (Shift 1)]

a

1120

b

1110

c

1210

d

1220

✓ Correct answer: a)

1120

Explanation

\(If the system of equations

2x+3y−z=5x+αy+3z=−43x−y+βz=7

has infinitely many solutions, then 13αβ is equal to

\begin{aligned}
&2=\mathrm{k}_1+3 \mathrm{k}_2, 3=\mathrm{k}_1 \alpha-\mathrm{k}_2,-1=3 \mathrm{k}_1+\beta \mathrm{k}_2,-5=4 \mathrm{k}_1-7 \mathrm{k}_2\\
&\text { On solving we get }\\
&\begin{aligned}
& k_2=\frac{13}{19}, k_1=\frac{-1}{19}, \alpha=-70, \beta=\frac{-16}{13} \\
& 13 \alpha \beta=13(-70)\left(\frac{-16}{13}\right) \\
& =1120
\end{aligned}
\end{aligned}\)

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