Let the system of equations x+2 y+3 z=5, 2 x+3 y+z=9, 4 x+3 y+ z= have infinite number of solutions. Then +2 is equal to :
- 22
- 17
- 15
- 28
Answer
(2) 17
Solution
Since the system has infinitely many solutions, Cramer's rule needs = 1 = 2 = 3 = 0.
= vmatrix1&2&3\\2&3&1\\4&3& vmatrix = (3 - 3) - 2(2 - 4) + 3(6 - 12) = - - 13
so = 0 gives = -13.
Replacing the z-column by the constants,
3 = vmatrix1&2&5\\2&3&9\\4&3& vmatrix = (3 - 27) - 2(2 - 36) + 5(6 - 12) = 15 -
hence 3 = 0 gives = 15.
With = -13 and = 15, 1 and 2 also come out zero, and the first two equations are independent, so the system indeed has infinitely many solutions.
Therefore + 2 = -13 + 30 = 17
Answer: (2)