(x-1/2)(x²+1/4)(x+1/2)
=(x-1/2）x+1/2))(x²+1/4)
=（x²-1/4)(x²+1/4)
=x^4-1/16,
(-1-4a^2)这个已经计算好了吧~~
(2x-3y-1)(2x+3y-1)
=（2x-1-3y）（2x-1+3y）
=（2x-1）²-（3y）²
=4x²-4x+1-9y²
先化简后求值
(x-5y)(-x-5y)-(-x+5y)^2
x=0.5 y=-1
(x-5y)(-x-5y)-(-x+5y)^2
=-（x-5y)(x+5y)-(x-5y)²
=-x²+25y²-x²+10xy-25y²
=-2x²+10xy
=-2×0.5²+10×0.5×（-1）
=-2×0.25-5
-0.5-5
=-5.5