JEE 2023 — Mathematics PYQ
JEE | Mathematics | 2023For the system of equations
x+y+z=6
x+2y+αz=10
x+3y+5z=β,
which one of the following is NOT true :
Choose the correct answer:
- A.
System has a unique solution for α=3, β=14.
(Correct Answer) - B.
System has a unique solution for α=−3, β=14.
- C.
System has no solution for α=3, β=24.
System has a unique solution for α=3, β=14.
Explanation
For unique solution Δ=0
For infinitely many solutions Δ=Δ1=Δ2=Δ3=0
Δ1=<br><br>6<br>10<br>βamp;1amp;2amp;3amp;1amp;αamp;5<br><br>=6(10−3α)−(50−αβ)+(30−2β)<br>=40−18α+αβ−2β
Δ2=<br><br>1<br>1<br>1amp;6amp;10amp;βamp;1amp;αamp;5<br><br>=(50−αβ)−6(5−α)+(β−10)<br>=10+6α+β−αβ
Δ3=<br><br>1<br>1<br>1amp;1amp;2amp;3amp;6amp;10amp;β<br><br>=(2β−30)−(β−10)+6<br>=β−14
Δ=<br><br>1<br>1<br>1amp;1amp;2amp;3amp;1amp;αamp;5<br><br>=1(10−3α)−(5−α)+(3−2)<br>=6−2α
For infinitely many solutions
Δ=0, Δ1=0, Δ2=0, Δ3=0
α=3, β=14
For unique solution α ≠ 3
Explanation
For unique solution Δ=0
For infinitely many solutions Δ=Δ1=Δ2=Δ3=0
Δ1=<br><br>6<br>10<br>βamp;1amp;2amp;3amp;1amp;αamp;5<br><br>=6(10−3α)−(50−αβ)+(30−2β)<br>=40−18α+αβ−2β
Δ2=<br><br>1<br>1<br>1amp;6amp;10amp;βamp;1amp;αamp;5<br><br>=(50−αβ)−6(5−α)+(β−10)<br>=10+6α+β−αβ
Δ3=<br><br>1<br>1<br>1amp;1amp;2amp;3amp;6amp;10amp;β<br><br>=(2β−30)−(β−10)+6<br>=β−14
Δ=<br><br>1<br>1<br>1amp;1amp;2amp;3amp;1amp;αamp;5<br><br>=1(10−3α)−(5−α)+(3−2)<br>=6−2α
For infinitely many solutions
Δ=0, Δ1=0, Δ2=0, Δ3=0
α=3, β=14
For unique solution α ≠ 3

