x - y = 7 এবং xy = 15 হলে, (x + y) (x - y) এর মান কত ? 

A 501 

B 51982 

C 52982 

D 519 

Solution

Correct Answer: Option B

1st rashi : x+y = (x-y) + 2xy 

= 7+2.15 = 49 + 30 = 79 

2nd rashi : x - y = (x - y) + 3xy (x-y) 

= (7) + 3.15.7 = 343 + 315 = 658 

 (x + y ) (x - y) = 79 \( \times \)658 = 51982   

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