给定数据表如下[tex=16.571x3.357]OOdTrLGt+hva56tTPivt0/r95dokJkdKTk98EGDhBNUwwvPSMqQ9+aeTQ2HsKPWOMIJr4R70TDuHuiTv3S1DPYIPY/mUZJEpF6rOX0bRjPCH63WJeZvfe7ZF1QmFGDncn7MUuSV83DZa00IIMCd1Ja1NlRLKWMLWZCYXBRlqB+N2xKlpGU5wpqwdGr4l6XVT[/tex]（1）用三次插值多项式计算[tex=2.571x1.286]WXl7aTmBZwDKTODr4AwoZA==[/tex]的近似值；（2）用二次插值多项式计算[tex=3.071x1.286]deYvyFCZtS5temkeHqdoNA==[/tex]的近似值；（3）用分段二次插值计算[tex=1.857x1.286]G6WxJ307HB2e1l7Qz3uNbQ==[/tex]（[tex=5.643x1.286]lusWrymqw2MApyoeZ9LVlaG7RaNinVoGHvhuWZKCNLdwng78wI5DjlIpIwT/lExY[/tex]）的近似值能保证有几位有效数字（不计舍入误差）？其中已知[tex=9.714x1.714]a4Eg/bvBEa+RCCx/mnsgtyYoIQK6IBNiDvTBn/Riyu8+ZlHYT+JWvLAydi5Cak5hpQzKmCFCR1NnV40o4yUpRQ==[/tex]。