x^2-x+1/4=x²-2x×1/2+(1/2)²=(x-1/2)² x^2-6x+9 =x²-2×x×3+3²=(x-3)²25y^2-80y+64=(5y)²-2×5y×8+8²=(5y-8)²(x-y)^2-10(x-y)+25 =[(x-y)-5]²=(x-y-5)²-...