If the system of linear equations : … is consistent and has infinite number of solutions, then :
JEE Main 2013 — Mathematics Algebra
2013mcqeasy
If the system of linear equations : x1+2x2+3x3=6x1+3x2+5x3=92x1+5x2+ax3=b is consistent and has infinite number of solutions, then :
Official previous-year question
Held on 22 Apr 2013 · Verified 6 Jul 2026.
Options
A
a=8,b can be any real number
B
b=15,a can be any real number
C
a∈R−{8} and b∈R−{15}
D
a=8,b=15
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Solution
Given system of equations can be written in matrix form as AX=B where A=11223535a and B=69b Since, system is consistent and has infinitely many solutions ∴(adj.A)B=0⇒3a−2510−a−115−2aa−6−11−2169b=000⇒−6−9+b=0⇒b=15 and 6(10−a)+9(a−6)−2(b)=0⇒60−6a+9a−54−30=0⇒3a=24⇒a=8 Hence, a=8,b=15.
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