一元二次方程：2y²=5解出来等于正负根号10/2，根号10怎么得出来的？还有（x-10）²=3 解下列一元二次方程
\u4e00\u5143\u4e8c\u6b21\u65b9\u7a0b\u7684\u9898\u4e00\u5143\u4e8c\u6b21\u65b9\u7a0b\u5e94\u7528\u7684\u8bdd\uff0c\u4e5f\u5c31\u8fd9\u51e0\u79cd\u7c7b\u578b\u4e86\u3002\u3002\u3002\u65b9\u6cd5\u638c\u63e1\u4e86\uff0c\u600e\u4e48\u53d8\u90fd\u4e0d\u6015\u3002
\u4e00\u3001\u589e\u957f\u7387\u95ee\u9898
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\u89e3\u3000\u8bbe\u8fd9\u4e24\u4e2a\u6708\u7684\u5e73\u5747\u589e\u957f\u7387\u662fx.\uff0c\u5219\u6839\u636e\u9898\u610f\uff0c\u5f97200(1\uff0d20%)(1+x)2\uff1d193.6\uff0c
\u5373(1+x)2\uff1d1.21\uff0c\u89e3\u8fd9\u4e2a\u65b9\u7a0b\uff0c\u5f97x1\uff1d0.1\uff0cx2\uff1d\uff0d2.1\uff08\u820d\u53bb\uff09.
\u7b54\u3000\u8fd9\u4e24\u4e2a\u6708\u7684\u5e73\u5747\u589e\u957f\u7387\u662f10%.
\u8bf4\u660e\u3000\u8fd9\u662f\u4e00\u9053\u6b63\u589e\u957f\u7387\u95ee\u9898\uff0c\u5bf9\u4e8e\u6b63\u7684\u589e\u957f\u7387\u95ee\u9898\uff0c\u5728\u5f04\u6e05\u695a\u589e\u957f\u7684\u6b21\u6570\u548c\u95ee\u9898\u4e2d\u6bcf\u4e00\u4e2a\u6570\u636e\u7684\u610f\u4e49\uff0c\u5373\u53ef\u5229\u7528\u516c\u5f0fm(1+x)2\uff1dn\u6c42\u89e3\uff0c\u5176\u4e2dm\uff1cn.\u5bf9\u4e8e\u8d1f\u7684\u589e\u957f\u7387\u95ee\u9898\uff0c\u82e5\u7ecf\u8fc7\u4e24\u6b21\u76f8\u7b49\u4e0b\u964d\u540e\uff0c\u5219\u6709\u516c\u5f0fm(1\uff0dx)2\uff1dn\u5373\u53ef\u6c42\u89e3\uff0c\u5176\u4e2dm\uff1en.
\u4e8c\u3001\u5546\u54c1\u5b9a\u4ef7
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\u89e3\u3000\u6839\u636e\u9898\u610f\uff0c\u5f97(a\uff0d21)(350\uff0d10a)\uff1d400\uff0c\u6574\u7406\uff0c\u5f97a2\uff0d56a+775\uff1d0\uff0c
\u89e3\u8fd9\u4e2a\u65b9\u7a0b\uff0c\u5f97a1\uff1d25\uff0ca2\uff1d31.
\u56e0\u4e3a21\u00d7(1+20%)\uff1d25.2\uff0c\u6240\u4ee5a2=31\u4e0d\u5408\u9898\u610f\uff0c\u820d\u53bb.
\u6240\u4ee5350\uff0d10a\uff1d350\uff0d10\u00d725\uff1d100\uff08\u4ef6\uff09.
\u7b54\u3000\u9700\u8981\u8fdb\u8d27100\u4ef6\uff0c\u6bcf\u4ef6\u5546\u54c1\u5e94\u5b9a\u4ef725\u5143.
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\u4e09\u3001\u50a8\u84c4\u95ee\u9898
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\u89e3\u3000\u8bbe\u7b2c\u4e00\u6b21\u5b58\u6b3e\u65f6\u7684\u5e74\u5229\u7387\u4e3ax.
\u5219\u6839\u636e\u9898\u610f\uff0c\u5f97[1000(1+x)\uff0d500](1+0.9x)\uff1d530.\u6574\u7406\uff0c\u5f9790x2+145x\uff0d3\uff1d0.
\u89e3\u8fd9\u4e2a\u65b9\u7a0b\uff0c\u5f97x1\u22480.0204\uff1d2.04%\uff0cx2\u2248\uff0d1.63.\u7531\u4e8e\u5b58\u6b3e\u5229\u7387\u4e0d\u80fd\u4e3a\u8d1f\u6570\uff0c\u6240\u4ee5\u5c06x2\u2248\uff0d1.63\u820d\u53bb.
\u7b54\u3000\u7b2c\u4e00\u6b21\u5b58\u6b3e\u7684\u5e74\u5229\u7387\u7ea6\u662f2.04%.
\u8bf4\u660e\u3000\u8fd9\u91cc\u662f\u6309\u6559\u80b2\u50a8\u84c4\u6c42\u89e3\u7684\uff0c\u5e94\u6ce8\u610f\u4e0d\u8ba1\u5229\u606f\u7a0e.
\u56db\u3001\u8da3\u5473\u95ee\u9898
\u4f8b4\u3000\u4e00\u4e2a\u9189\u6c49\u62ff\u7740\u4e00\u6839\u7af9\u7aff\u8fdb\u57ce\uff0c\u6a2a\u7740\u600e\u4e48\u4e5f\u62ff\u4e0d\u8fdb\u53bb\uff0c\u91cf\u7af9\u7aff\u957f\u6bd4\u57ce\u95e8\u5bbd4\u7c73\uff0c\u65c1\u8fb9\u4e00\u4e2a\u9189\u6c49\u5632\u7b11\u4ed6\uff0c\u4f60\u6ca1\u770b\u57ce\u95e8\u9ad8\u5417\uff0c\u7ad6\u7740\u62ff\u5c31\u53ef\u4ee5\u8fdb\u53bb\u5566\uff0c\u7ed3\u679c\u7ad6\u7740\u6bd4\u57ce\u95e8\u9ad82\u7c73\uff0c\u4e8c\u4eba\u6ca1\u529e\u6cd5\uff0c\u53ea\u597d\u8bf7\u6559\u806a\u660e\u4eba\uff0c\u806a\u660e\u4eba\u6559\u4ed6\u4eec\u4e8c\u4eba\u6cbf\u7740\u95e8\u7684\u5bf9\u89d2\u659c\u7740\u62ff\uff0c\u4e8c\u4eba\u4e00\u8bd5\uff0c\u4e0d\u591a\u4e0d\u5c11\u521a\u597d\u8fdb\u57ce\uff0c\u4f60\u77e5\u9053\u7af9\u7aff\u6709\u591a\u957f\u5417\uff1f
\u89e3\u3000\u8bbe\u6e20\u9053\u7684\u6df1\u5ea6\u4e3axm\uff0c\u90a3\u4e48\u6e20\u5e95\u5bbd\u4e3a(x+0.1)m\uff0c\u4e0a\u53e3\u5bbd\u4e3a(x+0.1+1.4)m.
\u5219\u6839\u636e\u9898\u610f\uff0c\u5f97(x+0.1+x+1.4+0.1)\u00b7x\uff1d1.8\uff0c\u6574\u7406\uff0c\u5f97x2+0.8x\uff0d1.8\uff1d0.
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\u6240\u4ee5x+1.4+0.1\uff1d1+1.4+0.1\uff1d2.5.
\u7b54\u3000\u6e20\u9053\u7684\u4e0a\u53e3\u5bbd2.5m\uff0c\u6e20\u6df11m.
\u8bf4\u660e\u3000\u6c42\u89e3\u672c\u9898\u5f00\u59cb\u65f6\u597d\u8c61\u65e0\u4ece\u4e0b\u7b14\uff0c\u4f46\u53ea\u8981\u80fd\u4ed4\u7ec6\u5730\u9605\u8bfb\u548c\u53e3\u5473\uff0c\u5c31\u80fd\u4ece\u4e2d\u627e\u5230\u7b49\u91cf\u5173\u7cfb\uff0c\u5217\u51fa\u65b9\u7a0b\u6c42\u89e3.
\u4e94\u3001\u53e4\u8bd7\u95ee\u9898
\u4f8b5\u3000\u8bfb\u8bd7\u8bcd\u89e3\u9898\uff1a\uff08\u901a\u8fc7\u5217\u65b9\u7a0b\u5f0f\uff0c\u7b97\u51fa\u5468\u745c\u53bb\u4e16\u65f6\u7684\u5e74\u9f84\uff09.
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\u5219\u6839\u636e\u9898\u610f\uff0c\u5f97x2\uff1d10(x\uff0d3)+x\uff0c\u5373x2-11x+30\uff1d0\uff0c\u89e3\u8fd9\u4e2a\u65b9\u7a0b\uff0c\u5f97x\uff1d5\u6216x\uff1d6.
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\u5f53x\uff1d6\u65f6\uff0c\u5468\u745c\u5e74\u9f84\u4e3a36\u5c81\uff0c\u5b8c\u5168\u7b26\u5408\u9898\u610f.
\u7b54\u3000\u5468\u745c\u53bb\u4e16\u7684\u5e74\u9f84\u4e3a36\u5c81.
\u8bf4\u660e\u3000\u672c\u9898\u867d\u7136\u662f\u4e00\u9053\u53e4\u8bd7\u95ee\u9898\uff0c\u4f46\u5b83\u6d89\u53ca\u5230\u6570\u5b57\u548c\u5e74\u9f84\u95ee\u9898\uff0c\u901a\u8fc7\u6c42\u89e3\u540c\u5b66\u4eec\u5e94\u4ece\u4e2d\u8ba4\u771f\u53e3\u5473.
\u516d\u3001\u8c61\u68cb\u6bd4\u8d5b
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\u7b54\u3000\u53c2\u52a0\u6bd4\u8d5b\u7684\u9009\u624b\u5171\u670945\u4eba.
\u8bf4\u660e\u3000\u7c7b\u4f3c\u4e8e\u672c\u9898\u4e2d\u7684\u8c61\u68cb\u6bd4\u8d5b\u7684\u5176\u5b83\u4f53\u80b2\u6bd4\u8d5b\u6216\u4e92\u8d60\u8d3a\u5e74\u7247\u7b49\u95ee\u9898\uff0c\u90fd\u53ef\u4ee5\u4eff\u7167\u4e9b\u65b9\u6cd5\u6c42\u89e3.
\u4e03\u3001\u60c5\u666f\u5bf9\u8bdd
\u4f8b7\u3000\u6625\u79cb\u65c5\u884c\u793e\u4e3a\u5438\u5f15\u5e02\u6c11\u7ec4\u56e2\u53bb\u5929\u6c34\u6e7e\u98ce\u666f\u533a\u65c5\u6e38\uff0c\u63a8\u51fa\u4e86\u5982\u56fe1\u5bf9\u8bdd\u4e2d\u6536\u8d39\u6807\u51c6.
\u67d0\u5355\u4f4d\u7ec4\u7ec7\u5458\u5de5\u53bb\u5929\u6c34\u6e7e\u98ce\u666f\u533a\u65c5\u6e38\uff0c\u5171\u652f\u4ed8\u7ed9\u6625\u79cb\u65c5\u884c\u793e\u65c5\u6e38\u8d39\u752827000\u5143.\u8bf7\u95ee\u8be5\u5355\u4f4d\u8fd9\u6b21\u5171\u6709\u591a\u5c11\u5458\u5de5\u53bb\u5929\u6c34\u6e7e\u98ce\u666f\u533a\u65c5\u6e38\uff1f
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\u5219\u6839\u636e\u9898\u610f\uff0c\u5f97[1000\uff0d20(x\uff0d25)]x\uff1d27000.
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\uff081\uff09x²+5x+7=3x+11
x²+2x=4
(x+1)²=5
x+1=\u00b1\u221a5
x=-1\u00b1\u221a5
\uff082\uff09x(2x-5)=4x-10
2x²-5x=4x-10
2x²-9x+10=0
(2x-5)(x-2)=0
x1=2 x2=2.5
\uff083\uff092x²+5x+7=-3x+11
2x²+8x=4
x²+4x=2
(x+2)²=6
x+2=\u00b1\u221a6
x=-2\u00b1\u221a6
\uff084\uff09x(x-1)=3x+7
x²-x=3x+7
x²-4x=7
(x-2)²=11
x-2=\u00b1\u221a11
x=2\u00b1\u221a11
（x-10）²=3 ，则x-10=正负√3 ，于是：x=10+√3 或 x=10-√3
一元二次方程ax^2+bx+c=0的求根公式为：
x=(-b±√b^2-4ac)/2a （b^2-4ac>=0时才能用）俗称万能公式
平方根，又叫二次方根，对于非负实数来说，是指某个自乘结果等于的实数，表示为〔√￣〕，其中属于非负实数的平方根称算术平方根。一个正数有两个平方根；0只有一个平方根，就是0本身；负数没有平方根。 例：9的平方根是±3
平方根_百度百科
http://baike.baidu.com/view/229977.htm
2y²=5
=>y²=(5/2)=10/2²
=>y=±〔√10￣〕/2
x-10）²=3
=>x-10=±〔√3￣〕
=>x=10±〔√3￣〕
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