\u4e0b\u56fe\u6570\u5b66\u8bb2\u89e3

1,
(1)\u82e5b\uff1e0\uff0c\u5219a+b\uff1ea-b
\u82e5b=0\uff0c\u5219a+b=a-b
\u82e5b\uff1c0\uff0c\u5219a+b\uff1ca-b
(2)\u82e5a\u2265b\uff0c\u5219 |a-b|=a-b
\u82e5a\uff1cb\uff0c\u5219 |a-b|\uff1ea-b
2,
\u539f\u5f0f\u7684\u5012\u6570\u4e3a(1/6-3/14+2/3-2/7)\u00f7(-1/42)
=(1/6-3/14+2/3-2/7)\u00d7(-42)
=(1/6)\u00d7(-42)-(3/14)\u00d7(-42)+(2/3)\u00d7(-42)-(2/7)\u00d7(-42)
= -7+9-28+12
= -14
\u6240\u4ee5\u539f\u5f0f= -1/14

(40x8-(300-68+13))/(8-5)=25
40-25=15
\u82e5\u627e\u56de68\u5143\u5219\u7528\u53bb232\u5143
(40x8-232)/(8-5)\u7684\u503c\u4e0d\u662f\u6574\u6570\uff0c\u6240\u4ee5\u4e0d\u53ef\u80fd\u3002