一條幾難既數~

1.1082﹣16x108+63
=1082﹣2x108x8+82﹣1
=(108﹣8)2﹣1
=1002﹣12
=(100+1)(100﹣1)=9999

2.99999992
= (1000000﹣1)2
= 1000000000000﹣2(1000000) + 1
= 1000000000000﹣2000000 + 1
= 999998000001

a2﹣b2 = (a﹣b)(a+b)

1)
你大可以用factorization就可以
108^2-16x108+63很明顯是
(108-9)(108-7)
=99x101
=9900+99=9999
2)9999999^2
=(10000000-1)^2
by using (a-1)^2=a^2-2a+1
=(10000000)^2-2(10000000)+1
=100,000,000,000,000-2000000+1
=99,999,980,000,001

(A-B)^2=A^2-2AB+B^2
1.108^2-16X108+63
=(108)^2-(2)(108)(8)+(8)^2-1
=(108-8)^2-1
=100^2-1
=9999

2.9999999^2
=(10000000-1)^2
=10000000^2-(2)(10000000)(1)+1
=100000000000000-20000000+1
=99999980000000+1
=99999980000001

2007-11-22 18:28:27 補充：
NCY呢個解答者唔知係唔係睇錯QUESTION......個題目有7個9,佢寫9999999=(1000000-1)

2007-11-22 18:29:26 補充：
佢個個"1000000"少左個0,應該係"10000000"