If a + b + c = 13 and ab + bc + ca = 45, find a2 + b2 + c2.
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 79.
(a + b + c)2 = a2 + b2 + c2 + 2(ab + bc + ca)
According to the given question,
⇒ 132 = a2 + b2 + c2 + 2(45)
⇒ a2 + b2 + c2 = 169 - 90
⇒ a2 + b2 + c2 = 79