(1)704×696 (2)(x+2y)(x-2y)+(x+1)(x-1) (3)x(x-1)-(x-31)(x+31)

问题描述:

(1)704×696 (2)(x+2y)(x-2y)+(x+1)(x-1) (3)x(x-1)-(x-31)(x+31)

(1)704×696
=(700+4)(700-4)
=700²-4²
=490000-16
=489984
(2)(x+2y)(x-2y)+(x+1)(x-1)
=x²-4y²+x²-1
=2x²-4y²-1
(3)x(x-1)-(x-31)(x+31)
=x²-x-(x²-31²)
=x²-x-x²+961
=-x+961