If the system of linear equations : x+y+z=6, x+2y+5z=10, 2x+3y+ z= has infinitely many solutions, then the value of + equals :
- 12
- 16
- 22
- 28
Answer
(3) 22
Solution
For infinitely many solutions: =0 and the third equation must not contradict the first two
= vmatrix1 & 1 & 1\ 1 & 2 & 5\ 2 & 3 & vmatrix=1(2 -15)-1( -10)+1(3-4)= -6
=0 =6
Adding the first two equations: 2x+3y+6z=16
the third equation 2x+3y+6z= is consistent (dependent) only when =16
+ =6+16=22
Answer: (3)