广发银行个人贷款申请:一道初2的计算题,怎么算也算不对......

来源:百度文库 编辑:神马品牌网 时间:2024/05/13 11:21:41
(2倍根号7 +5)^2*(5- 2倍根号7)^2

我怎么算得-3呢???

(25-2*2*7)^2=(-3)^2=9

(5+2√7)^2 * (5-2√7)^2
=[(5+2√7)(5-2√7)]^2
=[5^2 - (2√7)^2]^2
=(25-28)^2
=9