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JEE Main 20209 JanuaryEvening Shift
Exam
JEE Main
Year
2020
Date
9 January
Shift
Evening Shift
Subject
Mathematics
Chapter
Determinants

JEE Main 2020 · 9 January · Evening Shift · Mathematics · Determinants

The following system of linear equations 7x + 6y - 2z = 0 3x + 4y +...

The following system of linear equations
7x+6y−2z=07x + 6y - 2z = 0
3x+4y+2z=03x + 4y + 2z = 0
x−2y−6z=0,x - 2y - 6z = 0, has

Options

  1. Ainfinitely many solutions, (x,y,z)\left(x, y, z\right) satisfying y=2zy = 2z
  2. Bno solution
  3. Cinfinitely many solutions, (x,y,z)\left(x, y, z\right) satisfying x=2zx = 2z
  4. Donly the trivial solution

Correct answer

C. infinitely many solutions, (x,y,z)\left(x, y, z\right) satisfying x=2zx = 2z

Step-by-step solution

\left|\begin{cases}7 & 6 & - 2 \\ 3 & 4 & 2 \\ 1 & - 2 & - 6\end{cases}\right|

=7(−20)−6(−20)−2(−10)</p><p>= 7 \left(- 20\right) - 6 \left(- 20\right) - 2 \left(- 10\right)</p><p>= - 140 + 120 + 20 = 0</p><p>Soinfinitenon−trivialsolutionexist<br/>Nowequation</p><p>So infinite non-trivial solution exist<br />Now equation( 1 ) + 3equationequation( 3 )<br/><br />⇒ 10x - 20z = 0<br/>⇒x=2z<br />⇒ x = 2z

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