x + y + z = 2 and xy + yz + zx = -11, then the value of x2 + y2 + z2 -3xyz is :
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 74
x + y + z = 2 and xy + yz + zx = -11
x2 + y2 + z2 -3xyz = (x + y + z)[(x + y + z)2 - 3(xy + yz + zx)] ---- (1)
Using equation (1), we get
⇒ 2[(2)2 - 3(-11)]
⇒ 2 [4 - (-33)]
⇒ 2(4 + 33)
⇒ 2 (37)
⇒ 74