If the system of linear equations x-2y+z=-4 2x+ y+3z=5 3x-y+ z=3 has infinitely many solutions, then 12 +13 is equal to
- 60
- 54
- 64
- 58
Answer
(4) 58
Solution
For infinitely many solutions, D = D1 = D2 = D3 = 0 (Cramer's rule).
D2 = vmatrix 1 & -4 & 1 \ 2 & 5 & 3 \ 3 & 3 & vmatrix = (5 - 9) + 4(2 - 9) + (6 - 15) = 13 - 54
D2 = 0 gives = 5413.
D = vmatrix 1 & -2 & 1 \ 2 & & 3 \ 3 & -1 & vmatrix = ( + 3) + 2(2 - 9) + (-2 - 3 ) = - 3 + 4 - 17
Putting = 5413 in D = 0: ( 5413 - 3 ) = 17 - 21613, i.e. 15 13 = 513, so = 13
With these values D1 = D3 = 0 as well, so the system indeed has infinitely many solutions.
12 + 13 = 4 + 54 = 58
Answer: (4)