a + b + c = 15, a2 + b2 + c2 = 83 হলে ab + bc + ca =?
Solution
Correct Answer: Option A
দেওয়া আছে,
a + b + c = 15
a2 + b2 + c2 = 83
আমরা জানি
(a + b + c)2 = a2 + b2 + c2 + 2(ab + bc + ca)
⇒ 152 = 83 + 2(ab + bc + ca)
⇒ 225 - 83 = 2(ab + bc + ca)
⇒ 2(ab + bc + ca) = 142
⇒ (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)
⇒ 152 = 83 + 2(ab + bc + ca)
⇒ 225 - 83 = 2(ab + bc + ca)
⇒ 2(ab + bc + ca) = 142
⇒ (ab + bc + ca) = 142/2
∴ (ab + bc + ca) = 71
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