十字相乘法怎么用？
\u600e\u6837\u7528\u5341\u5b57\u76f8\u4e58\u6cd5ax2+bx+c \u8fd9\u662f\u4e00\u822c\u5f62\u5f0f\uff08a\u3001b\u3001c\u90fd\u662f\u5e38\u6570\uff0ca\u5fc5\u4e3a\u6b63\u53f7\u7684\uff0c\u8fd9\u662f\u6570\u5b66\u4e0a\u505a\u65b9\u7a0b\u7684\u5e38\u8bc6\uff0c\u8981\u5c06\u7c7b\u4f3c\u4e8e\u20146x2+8x+2\u7684\u5f0f\u5b50\uff0c\u8f6c\u53d8\u62106x2-8x-2\uff0c\u6240\u4ee5a\u5fc5\u4e3a\u6b63\u53f7\uff0c\u53e6\u5916\uff0c\u8fd9\u91cc\u6ca1\u53d1\u6253\u51fa\u5e73\u65b9\uff0c\u4f46\u662f\u4f60\u5e94\u8be5\u4e0d\u4f1a\u770b\u9519\u628a\u3002\uff09
\u9996\u5148,\u4e00\u822c\u9898\u76ee\u4e0d\u4f1a\u5f88\u53d8\u6001\u7684\u5c06\u4e8c\u6b21\u9879\u7684\u7cfb\u6570\uff08\u5373a\uff09\u641e\u5f97\u5f88\u5927\uff0c
\u6240\u4ee5\uff0c\u8fd9\u6709\u4e00\u5b9a\u7684\u8bc0\u7a8d\uff0c\u9996\u5148\u5217\u51faa\u7684\u6240\u6709\u56e0\u5b50\uff0c\u4f8b\u5982\uff0ca\u662f6\uff0c\u5219\u5217\u51fa\uff082\uff0c3\uff09
(1\uff0c6)\uff0c\u7136\u540e\u5bf9c\u4e5f\u4f5c\u540c\u6837\u5730\u5904\u7406\u3002\u63a5\u7740\uff0c\u770bb\uff0cc\u7684\u7b26\u53f7\u3002\u5982\u679c\uff0cb\u662f\u6b63\u53f7\uff0cc\u4e5f\u662f\u6b63\u53f7\uff0c\u90a3\u4e48\u6bd4\u8f83\u597d\u5904\u7406\uff0c\u628ac\u5206\u6210\u4e24\u4e2a\u6b63\u53f7\u7684\u56e0\u5b50\uff0c\u548ca\u7684\u56e0\u5b50\u51d1\u4e00\u51d1\uff08\u51d1\u5c31\u6ca1\u6709\u8bc0\u7a8d\u4e86\uff0c\u4e00\u822c\u4e0d\u4f1a\u8bd5\u5230\u592a\u591a\u6b21\u3002\u5982\u679c\u4f60\u521a\u5f00\u59cb\u5b66\u4f1a\u8fd9\u4e2a\uff0c\u5f53\u7136\u8fd8\u4e0d\u4f1a\u63a5\u89e6\u5230\u5c06a\uff0cc\u5206\u6210\u5e26\u6709\u5206\u6570\u4e24\u4e2a\u56e0\u6570\uff0c\u90a3\u65f6\u4e00\u5143\u4e8c\u6b21\u65b9\u7a0b\u624d\u5b66\u7684\uff09\u3002\u5982\u679cb\u65f6\u6b63\u53f7\uff0cc\u662f\u8d1f\u53f7\uff0c\u90a3\u4e48\uff0c\u4e00\u822c\u662f\u5c06c\u5206\u6210\u5dee\u8f83\u5927\u7684\u4e24\u4e2a\u56e0\u5b50\uff0c\u7136\u540e\u6b63\u53f7\u7ed9\u5927\u6570\uff0c\u4e0ea\u7684\u56e0\u5b50\u51d1\u3002
\u7136\u540e\uff0c\u5982\u679cb\u7684\u7b26\u53f7\u662f\u8d1f\u53f7\uff0c\u90a3\u4e48\u57fa\u672c\u6b65\u9aa4\u4e00\u6837\uff0c\u8981\u53cd\u4e00\u53cd\u7684\u5730\u65b9\u53cd\u4e00\u53cd\u3002
\u5c31\u50cf\u4f60\u7ed9\u7684\u8fd9\u9898\u3002\u9996\u51482\u53ea\u80fd\u5206\u62101*2\uff0c\u90a3\u4e48\u5148\u653e\u4e00\u8fb9\u3002\u7136\u540eb\u662f\u8d1f\u53f7\u7684\uff0c\u90a3\u4e48\u5c06c\u5206\u6210\u4e24\u4e2a\u5dee\u8f83\u5927\u7684\u56e0\u5b50\uff0c\u8fd9\u91cc\u5f53\u7136\u4e5f\u53ea\u80fd\u662f1\u30012\uff0c\u7531\u4e8eb\u662f\u8d1f\u7684\uff0c\u90a3\u4e48\u628a\u6b63\u53f7\u7ed9\u8f83\u5c0f\u7684\u6570\uff0c\u7136\u540e\u5217\u5f0f\u5b50\u3002
1 -2
*
2 1 2*(-2)+1*1=-3
\u5982\u679c\u4e0d\u5bf9\uff0c\u90a3\u4e48\u5c31\u8c03\u6574\u4e00\u4e0b\u4f4d\u7f6e\u3002\u53e6\u5916\uff0c\u8bb0\u4f4f\uff0c\u5217\u5982\u4e0a\u5f0f\u5b50\u65f6\uff0c\u662f\u4ea4\u53c9\u76f8\u4e58\uff1a1*1\uff0c2*-2\uff0c\u4f46\u662f\u5199\u5f0f\u5b50\u7684\u65f6\u5019\u8981\u6a2a\u7740\u5199\uff0c\uff081x-2\uff09\uff082-1\uff09\u6240\u4ee5\uff0c
2*(-2)+1*1=\uff081x-2\uff09\uff082-1\uff09\u5c31\u662f\u89e3\u3002
\u660e\u767d\u4e86\u5417\uff1f
\u89e3\u8fd9\u7c7b\u9898\uff0c\u6ca1\u6709\u4ec0\u4e48\u5fc5\u4f1a\u7684\u6280\u5de7\uff0c\u4ee5\u4e0a\u7684\u53ea\u662f\u4e00\u4e9b\u76ae\u6bdb\uff0c\u4f46\u53ef\u4ee5\u7ed9\u521d\u5b66\u8005\u8bb2\u89e3\uff0c\u5e76\u63d0\u9ad8\u521d\u5b66\u8005\u4e00\u5b9a\u7684\u89e3\u9898\u901f\u5ea6\uff0c\u6240\u4ee5\u8fd8\u662f\u8bb0\u4f4f\u4e3a\u597d\u3002
\u5728\u53c8\u95ee\u9898\u53bb\u8bf7\u6559\u6570\u5b66\u8001\u5e08\u597d\u4e86\uff0c\u4ed6\u4eec\u624d\u66f4\u6709\u7ecf\u9a8c\u3002
\u795d\u4f60\u597d\u8fd0\u3002
1/3-1/2=1/6 绝对值
3/5-1/2=1/10
a/b = 1/10 / 1/6
图：
1/3 1/10
1/2
3/5 1/6
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