10²-9²+8²-7²+6²-5²+4²-3²+2²-1²用简便算法啊,
问题描述:
10²-9²+8²-7²+6²-5²+4²-3²+2²-1²用简便算法啊,
答
(10-9)*(10+9) + (8-7)*(8+7) + (6+5)*(6-5) + (4+3)*(4-3)+(2-1)*(2+1)
=19 + 15 + 11 + 7 + 3
=(19 + 3)+ (15 + 7) + 11
= 22 +22 +11
= 55