a + b + c = 15 এবং a2 + b2 + c2 = 83 হলে ab + bc + ca = এর মান কত?
Solution
Correct Answer: Option C
দেয়া আছে,
a + b + c = 15
a2 + b2 + c2 = 83
আমরা জানি,
( a + b + c)2 = ( a2 + b2 + c2) + 2(ab + bc + ca)
⇒ (15)2 = 83 + 2(ab + bc + ca)
⇒ 2(ab + bc + ca) = 225 - 83
⇒ (ab + bc + ca) = 142/2
∴ (ab + bc + ca) = 71
a + b + c = 15
a2 + b2 + c2 = 83
আমরা জানি,
( a + b + c)2 = ( a2 + b2 + c2) + 2(ab + bc + ca)
⇒ (15)2 = 83 + 2(ab + bc + ca)
⇒ 2(ab + bc + ca) = 225 - 83
⇒ (ab + bc + ca) = 142/2
∴ (ab + bc + ca) = 71
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