1.Relation and Function
hard

माना $A=\{1,2,3,4, \ldots . .10\}$ और $B=\{0,1,2,3,4\}$ हैं। संबंध $\mathrm{R}=\left\{(\mathrm{a}, \mathrm{b}) \in \mathrm{A} \times \mathrm{A}: 2(\mathrm{a}-\mathrm{b})^2+\right.$ $3(\mathrm{a}-\mathrm{b}) \in \mathrm{B}\}$ में अवयवों की संख्या है______________

A

$12$

B

$14$

C

$16$

D

$18$

(JEE MAIN-2023)

Solution

$A=\{1,2,3, \ldots \ldots 10\}$

$B=\{0,1,2,3,4\}$

$R=\left\{(a, b) \in A \times A: 2(a-b)^2+3(a-b) \in B\right\}$

$\text { Now } 2(a-b)^2+3(a-b)=(a-b)(2(a-b)+3)$

$\Rightarrow a=b \text { or } a-b=-2$

Now $2(a-b)^2+3(a-b)=(a-b)(2(a-b)+3)$

$\Rightarrow a = b \text { or } a – b =-2$

When $a = b \Rightarrow 10$ order pairs

When $a-b=-2 \Rightarrow 8$ order pairs

Total $=18$

Standard 12
Mathematics

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