NVAEasyJEE 2024Sets & Operations

JEE Mathematics 2024 Question with Solution

Let the set CC = {(xx, yy) | x22y=2023x^2 - 2y = 2023, x,yNx, y \in N}. Then (x,y)C(x+y)\sum_{(x, y)\in C}(x + y) is equal to:

Answer

Correct answer:46

Step-by-step solution

Standard Method

Given: x22y=2023x^2 - 2^y = 2023 with x,yNx, y \in N.

Find: (x,y)C(x+y)\sum_{(x,y) \in C}(x+y).

From the solution working, test natural values of yy so that 2023+2y2023 + 2^y becomes a perfect square.

For y=1y = 1,

x2=2023+21=2025x^2 = 2023 + 2^1 = 2025

So,

x=2025=45x = \sqrt{2025} = 45

Thus, the solution in CC is (x,y)=(45,1)(x,y) = (45,1).

Now,

(x,y)C(x+y)=45+1=46\sum_{(x,y) \in C}(x+y) = 45 + 1 = 46

Therefore, the required numerical value is 4646.

Trial of Natural Values

Given: x22y=2023x^2 - 2^y = 2023.

Find: the value of (x,y)C(x+y)\sum_{(x,y) \in C}(x+y).

Rearrange the equation as

x2=2023+2yx^2 = 2023 + 2^y

We need the right-hand side to be a perfect square.

Trying the smallest natural value shown in the extracted solution,

y=1x2=2023+2=2025=452y=1 \Rightarrow x^2 = 2023 + 2 = 2025 = 45^2

Hence x=45x=45.

So the pair is (45,1)(45,1) and

x+y=45+1=46x+y = 45+1 = 46

Hence the sum over the set is 4646.

Common mistakes

  • Reading the equation as x22y=2023x^2 - 2y = 2023 instead of x22y=2023x^2 - 2^y = 2023. This changes the problem completely. Always preserve the exponent on 22 while interpreting the set definition.

  • Forgetting that x,yNx,y \in N. Negative or non-integer values are not allowed. Restrict the trial only to natural numbers.

  • Finding one valid pair and then reporting only xx or only yy. The question asks for (x,y)C(x+y)\sum_{(x,y)\in C}(x+y), so after identifying the pair, compute x+yx+y and then sum over all such pairs.

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