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1. The difference between two numbers is 7 and their product is 60, then one of the two numbers must be
- A. 4
- B. 4
- C. 4
- D. 4
Answer: Option B
Explanation:
ধরি, বড় সংখ্যা= x, ছোট সংখ্যা=y
প্রশ্নমতে, x - y =7……….(1)
xy =60 => x => 60/y
(1) নং এ x এর মান বসিয়ে পাই,
60/y - y =7
=> 60 - y2 - 7y =0
=> y2 +7y - 60= 0
=> y2 +12y -5y -60=0
=> y(y+12)-5(y+12)=0
=> (y+12)(y-5)=0
So, y = 5 but y≠-12
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