If (a + b + c) = 8 and (ab + bc + ca) = 19, find (a2 + b2 + c2)
It is given in the question that,
(a + b + c) = 8
And, (ab + bc + ca) = 19
We know that,
(a + b + c)2 = a2 + b2 + c2 + 2 (ab + bc + ca)
∴ (8)2 = a2 + b2 + c2 + 2 × 19
64 = a2 + b2 + c2 + 38
64 – 38 = a2 + b2 + c2
a2 + b2 + c2 = 26