[（4x-1/2y）的平方-4y（x+1/16y）]÷8x,其中x=-1/2,y=2
=[(-1/2*4-1/2*2)²-4*2(-1/2+1/16*2)]÷8*(-1/2)
=[(-3)²-8×(-1/2+1/8)]÷(-4)
=(9+3)÷(-4)
=-3