初一年级——根与系数的关系，求解

求解初一用十字相乘法分解因式的题

1。 2*（x+y）^2+(x+y)(c+d)-6（c+d）^2 =2(x+y)^2+4(x+y)(c+d)-3(x+y)(c+d)-6(c+d)^2 =2(x+y)((x+y)+2(c+d))-3(c+d)((x+y)+2(c+d)) =((x+y)+2(c+d))(2(x+y)-3(c+d)) 2。 21a^2-13ab+2b^2 =21a^2-7ab-6ab+2b^2 =7a(3a-b)-2b(3a-b) =(3a-b)(7a-2b) 3。 (x-y)^2-3(x-y)-10 =(x-y)^2-5(x-y)+2(x-y)-10 =(x-y)(x-y-5)+2(x-y-5) =(x...全部

  1。 2*（x+y）^2+(x+y)(c+d)-6（c+d）^2 =2(x+y)^2+4(x+y)(c+d)-3(x+y)(c+d)-6(c+d)^2 =2(x+y)((x+y)+2(c+d))-3(c+d)((x+y)+2(c+d)) =((x+y)+2(c+d))(2(x+y)-3(c+d)) 2。
   21a^2-13ab+2b^2 =21a^2-7ab-6ab+2b^2 =7a(3a-b)-2b(3a-b) =(3a-b)(7a-2b) 3。 (x-y)^2-3(x-y)-10 =(x-y)^2-5(x-y)+2(x-y)-10 =(x-y)(x-y-5)+2(x-y-5) =(x-y-5)(x-y+2) 4。
   x^(n+1)-3x^n+2x^(n+2) =x^n*x-3x^n+2x^n*x^2 =x^n(x-3+2x^2) =x^n(2x^2+3x-2x-3) =x^n(x(2x+3)-(2x+3)) =x^n(2x+3)(x-1) 。
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