(x-1)(x+ 2)等于多少啊?要过程呦,谢谢哥哥姐姐们! 已知(X+1)(X-3)分之2X-5=X+1分之A+X-3分...
-2x\uff08x-2y\uff09(x+2y\uff09\ufe63x\uff082x-y\uff09(y+2x)\uff0c\u5176\u4e2dx=1\uff0cy=2\u3002\u54e5\u54e5\u59d0\u59d0\u4eec\u5e2e\u5e2e\u5fd9\uff0c\u8981\u8fc7\u7a0b\u539f\u5f0f=-2x(x²-4y²)-x(4x²-y²)
=-2x³+8xy²-4x³+xy²
=-6x³+9xy²
=-6+36
=30
\u5c06\u7b49\u53f7\u540e\u9762\u7684\u5f0f\u5b50\u901a\u5206\u4e00\u4e0b\uff0c\u53d8\u4e3a\uff08X+1\uff09\uff08X-3)\u5206\u4e4b2X-5=\uff08X+1\uff09\uff08x-3)\u5206\u4e4b[A(x-3)+B(x+1)]\u6240\u4ee5\u5c31\u540c\u65f6\u5220\u53bb\u5206\u5f0f\u7684\u4e0b\u65b9\uff0c\u7559\u4e0b\u4e0a\u65b9\uff0c\u5c31\u53d8\u4e3a2x-5=Ax-3A+Bx+B\u6240\u4ee5\u5217\u65b9\u7a0bAx+Bx=2x \uff21\uff0b\uff22\uff1d\uff12 \u2016 \u2261\uff1d -3A+B=-5 \u3000\u3000\u3000\u3000\u3000\u3000\u3000\u3000\u3000\u3000\u3000\u3000\uff0d\uff13\uff21\uff0b\uff22\uff1d\uff0d\uff15\u3000\u6240\u4ee5\u53ef\u8ba1\u7b97\u5f97\u51faA\uff1d\uff0d�0�6\u3000\u3000\u3000\u3000\u3000\u3000\u3000B\uff1d\uff11\uff11\uff0f\uff14\u671b\u91c7\u7eb3\uff0c\u8c22\u8c22
①应用分配律,x乘(x+2)减去1乘(x+2),然后去括号,合并同类项,
②十字相乘法
(x-1)(x+ 2)
=x(x+2)-1(x+2)
=x^2+2x-x-2
=x^2+x-2
原式=x²+2x-x-2
=x²+x-2
(x-1)(x+2)
=Ⅹ²+2x-x-2
=ײ+×-2
(x²+2x)+(-x-2)=x²+x-2
扩展阅读:(x-2)(x-3) ... x(x+4)=8x+12 ... 1 2+2 2+3 2+ n 2 ... x-y 公式解析 ... x 3 ... x-1的n次方怎么展开 ... x-1 2 ... f(x) ... 1加到n的流程图 ...