+) (x+1)²-(x-1)²-3(x+1)(x-1)
=(x+1-x+1)(x+1+x-1)-3(x²-1)
=2×2x-3x²+3
=4x-3x²+3
+)5(x+2)(x-2)-$\frac{1}{2}$ (6-8x)²+17
= 5(x²-4)-$\frac{1}{2}$(36-96x+64x²)+17
=5x²-20-18+48x-32x²+17
=-27x²+48x-21
+)(2x-1)²+(x+1)²-5x(x+3)
= 4x²-4x+1+x²+2x+1-5x²-15x
=-17x+1
+) (x-2)(x+2)+2(2-x)²-4(x-2)(x+3)
=x²-4+2(4-4x+x²)-4(x²+3x-2x-6)
=x²-4+8-8x+2x²-4(x²+x-6)
=3x²-8x+4- 4x²-4x+24
=-x²-12+28