Factorizing the given expression gives:
−4a2+4ab−4ca
(4a2=2×2×a×a 4ab=2×2×a×b 4ca=2×2×c×a ∴−4a2+4ab−4ca=−(2×2×a×a)+(2×2×a×b)−(2×2×c×a) =2×2×a[−(a)+b−c] =4a(−a+b−c)