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1. $x + y = 7$

A. 7
B. 7
C. 7
D. 7

Answer: Option D

Explanation:

দেওয়া আছে, x + y = 7 x^{2} + y^{2} = 25 \Rightarrow {(x + y)}^{2} - 2 x y = 25 \Rightarrow 7^{2} - 25 = 2 x y \Rightarrow 2 x y = 49 - 25 \Rightarrow x y = \frac{24}{2} = 12 x^{3} + y^{3} = {(x + y)}^{3} - 3 x y (x + y) = 7^{3} - 3 \times 12 \times 7 = 343 - 252 = 91

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