∵x²+2x-2012=0
∴x²+2x = 2012
又：a、b是方程x²+2x-2012=0的两个实数根
∴a^2+2a = 2012,b^2+2b=2012
∴1/2a²-2b²+a-4b = 1/2(a^2+2a) - 2(b^2+2b) = 1/2*2012 - 2*2012 = -3/2*2012 = -3018