If a = 925, b = 924, c = 923, then
find 3(a2 + b2 + c2 - ab - bc - ca).
Answer & explanation
Correct answer: option 4
a2 + b2 + c2 - ab - bc - ca = \(\frac{1}{2}\) [(a - b)2 + (b - c)2 + (c - a)2]
= \(\frac{1}{2}\) [(925 - 924)2 + (924 - 923)2 + (923 - 925)2]
= \(\frac{1}{2}\) [1 + 1 + 4] = 3
= 3 × 3 = 9