(x³ - 2y³ - 3x²y)- (3x³ - 3y³ - 7x²y)原式 = x³ - 2y³ - 3x³y - 3x³ + 3y³ + 7x²y =(3+1)x³ + (-2+3)y³ + (-3+7)x²y= 4x³ + y³ + 4x²y这道题
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![(x³ - 2y³ - 3x²y)- (3x³ - 3y³ - 7x²y)原式 = x³ - 2y³ - 3x³y - 3x³ + 3y³ + 7x²y =(3+1)x³ + (-2+3)y³ + (-3+7)x²y= 4x³ + y³ + 4x²y这道题](/uploads/image/z/10380137-41-7.jpg?t=%EF%BC%88x%26%23179%3B+-+2y%26%23179%3B+-+3x%26%23178%3By%EF%BC%89-+%EF%BC%883x%26%23179%3B+-+3y%26%23179%3B+-+7x%26%23178%3By%EF%BC%89%E5%8E%9F%E5%BC%8F+%3D+x%26%23179%3B+-+2y%26%23179%3B+-+3x%26%23179%3By+-+3x%26%23179%3B+%2B+3y%26%23179%3B+%2B+7x%26%23178%3By+%3D%EF%BC%883%2B1%EF%BC%89x%26%23179%3B+%2B+%EF%BC%88-2%2B3%EF%BC%89y%26%23179%3B+%2B+%EF%BC%88-3%2B7%EF%BC%89x%26%23178%3By%3D+4x%26%23179%3B+%2B+y%26%23179%3B+%2B+4x%26%23178%3By%E8%BF%99%E9%81%93%E9%A2%98)
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(x³ - 2y³ - 3x²y)- (3x³ - 3y³ - 7x²y)原式 = x³ - 2y³ - 3x³y - 3x³ + 3y³ + 7x²y =(3+1)x³ + (-2+3)y³ + (-3+7)x²y= 4x³ + y³ + 4x²y这道题
(x³ - 2y³ - 3x²y)- (3x³ - 3y³ - 7x²y)
原式 = x³ - 2y³ - 3x³y - 3x³ + 3y³ + 7x²y
=(3+1)x³ + (-2+3)y³ + (-3+7)x²y
= 4x³ + y³ + 4x²y
这道题为什么结果是这样啊?这道题搞不懂.基础不好.
(x³ - 2y³ - 3x²y)- (3x³ - 3y³ - 7x²y)原式 = x³ - 2y³ - 3x³y - 3x³ + 3y³ + 7x²y =(3+1)x³ + (-2+3)y³ + (-3+7)x²y= 4x³ + y³ + 4x²y这道题
就是相同的加一块,遇到减号了,后面括号里面的要变号
(x³ - 2y³ - 3x²y)- (3x³ - 3y³ - 7x²y)
原式 = x³ - 2y³ - 3x³y - 3x³ + 3y³ + 7x²y
=(1-3)x³ + (-2+3)y³ + (-3+7)x²y
= -2x³ + y³ + 4x²y
这样才对呢
=(-3+1)x³
合并同类项出错了
第一步去括号
第二步配平 合并同类项
第三部总结
你弄错了吧,应该是(1-3)X3+(-2+3)y3+(-3+7)X2y才对,
答案应该是-2X3+y3+4X2y
第二步的(3+1)x³ 错了。应该是(-3+1)x³
第三步错了
3+1应该为1-3