If a + b - c = 5 and ab - bc - ac = 10, then find the value of a2 + b2 + c2.
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 5.
(a + b - c)2 = a2 + b2 + c2 + 2(ab - bc - ca) ---- (1)
Using equation (1), we get
⇒ 25 = a2 + b2 + c2 + 2(10)
⇒ a2 + b2 + c2 = 25 - 20 = 5