If a + b + c = 10 and ab + bc + ca = 30, then the value of a2 + b2 + c2 is:
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 40
We know that
(a + b + c)2 = a2 + b2 + c2 + 2(ab + bc + ac)
⇒ (10)2 = a2 + b2 + c2 + 2 × 30
⇒ 100 - 60 = a2 + b2 + c2
⇒ a2 + b2 + c2 = 40