九年级数学

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2 | 2013-9-2 07:19:27 | 显示全部楼层 |阅读模式

20. x2-16x+55=(x-5)(x-11) =0x = 5 或11因为5和11是两条直角边斜边 = √(52+112) = √14621. Bx2+4x+3 = 0用根与系数的关系得到 x1x2 = 3/1 = 3或者原式为 (x+1)(x+3)=0x = -1或-3x1*x2 = 322. Dx(x-2)+x-2 =0(x+1)(x-2) =0x =2或-123. 添项法因为9x11 = 99所以原方程为(x+9)(x-11)=0x = 11或 -9...

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