- Home
- Standard 12
- Mathematics
1.Relation and Function
normal
Let $A=\{1,2,3,4\}$ and $R$ be a relation on the set $A \times A$ defined by $R=\{((a, b),(c, d)): 2 a+3 b=4 c+5 d\}$. Then the number of elements in $R$ is:
A
$6$
B
$5$
C
$4$
D
$3$
(JEE MAIN-2023)
Solution
$A =\{1,2,3,4\}$
$R =\{( a , b ),( c , d )\}$
$2 a +3 b =4 c +5 d =\alpha \text { let }$
$2 a =\{2,4,6,8\} \quad 4 c =\{4,8,12,16\}$
$3 b =\{3,6,9,12\} \quad 5 d =\{5,10,15,20\}$
$2 a +3 b =\left\{\begin{array}{l}5,8,11,14 \\ 7,10,13,16 \\ 9,12,15,18 \\ 11,14,17,20\end{array}\right\} \quad 4 c +5 d \left\{\begin{array}{l}9,14,19,24 \\ 13,18 \ldots . \\ 17,22 \ldots \\ 21,26 \ldots\end{array}\right\}$
Possible value of $\alpha=9,13,14,14,17,18$
Pairs of $\{( a , b ),( c , d )\}=6$
Standard 12
Mathematics