যদি x - y = 1, xy = 56 হয় তবে x + y = কত ?
Correct Answer: Option C
দেওয়া আছে,
x - y = 1।, xy = 56
⇒ (x - y)2 = x2 + y2 - 2xy
⇒ 1 = x2 + y2 - 112
⇒ 1 + 112 = x2 + y2
⇒ x2 + y2 = 113
⇒ (x + y)2 = 113 + 112= 225
∴ x + y = 15
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