x²+7x-8=(x+8)(x-1)
x +8
x -1等等,别用图啊,用过程啊这就是十字相乘法的过程啊。+8*(-1)=-8+8+(-1)=7所以:x²+7x-8=(x+8)(x-1)我们老师是说用像分解因式一样的步骤,大哥帮帮吧,20分x²+7x-8=(x+8)(x-1)这就是步骤。好吧我再描述清楚点,老师给了一个公式 X²+(a+b)+ab=(x+a)(X+b),但我没搞懂x²+7x-8里的8在 ab里是怎么乘得的啊,这样看应该是用加-1得的7啊。。。。。我抄错了???-8=8×(-1)8+(-1)=7
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