Question

这三题怎么做啊？请写出详细步骤及所使用乘法公式

Answer 1

1. x²+2xy-8y²+2x+14y-3=(x²+2xy+y²)+(2x+2y)+1-(9y²-12y+4)
   =[(x+y)²+2(x+y)+1]-(3y-2)²
   =(x+y+1)²-(3y-2)²
   =[(x+y+1)-(3y-2][(x+y+1)+(3y-2)]
   =(x-2y+3)(x+4y-1)

2. x²-2(m-n)x+m²-2mn-3n²=x²-2(m-n)x+(m-n)²-4n²

   =(x-m+n)²-(2n)²=(x-m+n-2n)(x-m+n+2n)

   =(x-m-n)(x-m+3n)

3. (2a²-3a+1)x²-(3a-4)x-5=(2a-1)(a-1)x²-(3a-4)-5=[(2a-1)x-5][(a-1)x+1]