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