数学好的哥哥姐姐帮个忙~~
\u8c01\u6570\u5b66\u597d,\u5e2e\u4e2a\u5fd9\uff01\uff01\uff01\u7532\u3001\u4e59\u4e24\u4eba\u5206\u522b\u4ece\u8ddd\u76ee\u7684\u57306km\u548c10km\u7684\u4e24\u5730\u540c\u65f6\u51fa\u53d1,\u7532\u3001\u4e59\u7684\u901f\u5ea6\u6bd4\u662f3:4,\u7ed3\u7532\u6bd4\u4e59\u63d0\u524d20min\u5230\u8fbe\u76ee\u7684\u5730.\u6c42\u7532\u3001\u4e59\u7684\u901f\u5ea6\uff0e
20\u5206=1/3\u5c0f\u65f6
\u89e3\uff1a\u8bbe\u7532\u901f\u662fx\u5343\u7c73/\u5c0f\u65f6\uff0c\u5219\u4e59\u901f\u662f4/3x\u5343\u7c73/\u5c0f\u65f6
10/(4/3x)-6/x=1/3
7.5/x-6/x=1/3
1.5/x=1/3
x/4.5
4/3x=6
\u7b54\uff1a\u7532\u901f\u662f4.5\u5343\u7c73/\u5c0f\u65f6\uff0c\u4e59\u901f\u662f6\u5343\u7c73/\u5c0f\u65f6
1\u3001-x²-2y²-2x+8y+9
=-x²-2x-1 -2y²+8y-8 +18
=-(x+1)² -2(y-2)² +18
\u8be5\u4ee3\u6570\u5f0f\u7684\u6700 \u5927 \u503c\u662f 18 \uff0c\u5176\u4e2d x=-1 y=2\u3002
2\u3001a²+b²+c²-ab+bc+ac
=(2a²+2b²+2c²-2ab+2bc+2ac)/2
=(a²+b²-2ab b²+c²+2bc a²+c²+ac)/2
=[(a-b)² + (b+c)² + (a+c)²]/2
=(4002² +1 +4003²)/2
\u672c\u4eba\u8ba4\u4e3a\u8be5\u9898\u4e0d\u662fa\u3001b\u3001c\u503c\u7684\u6b63\u8d1f\u6709\u95ee\u9898\uff0c\u5c31\u662f\u4ee3\u6570\u5f0f\u7684ab\u548cac\u7684\u6b63\u8d1f\u53cd\u4e86\u3002
3\u3001m²+m-1=0 \u63a8\u51fa m²+m=1\uff1b
m³+2m²-2001
=m(m²+2m)-2001
=m(m²+m+m)-2001
=m(m+1)-2001
=m²+m-2001
=1-2001
=-2000
4\u3001x²-3x-2=0
x²-3x=2
[(x-1)³-x²+1]/(x-1)
=[(x-1)³-(x²-1)]/(x-1) \u2026\u2026(x²-1)=(x+1)(x-1)
=(x-1)²-(x+1)
=x²-2x+1-x-1
=x²-3x
=2
去 看看向量的书 知道向量向量相加就可以了
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