If the system of equations 11x + y + z = -5 2x + 3y + 5z = 3 8x - 19y - 39z = has infinitely many solutions, then 4 - is equal to :
- 51
- 45
- 47
- 49
Answer
(3) 47
Solution
For infinitely many solutions, = 0 and 1 = 0 (Cramer's rule).
= vmatrix 11 & 1 & \ 2 & 3 & 5 \ 8 & -19 & -39 vmatrix = 11(-117 + 95) - 1(-78 - 40) + (-38 - 24)
= -124 - 62 = 0 = -2
1 = vmatrix -5 & 1 & -2 \ 3 & 3 & 5 \ & -19 & -39 vmatrix = -5(-22) - 1(-117 - 5 ) - 2(-57 - 3 )
= 341 + 11 = 0 = -31
4 - = 16 + 31 = 47
Answer: (3)