Question

因式分解 求大神

Answer 1

9(x-y)²+12(x²-y²)+4(x+y)²
=[3(x-y)]²+2·3(x-y)·2(x+y)+[2(x+y)]²
=[3(x-y)+2(x+y)]²
=(3x-3y+2x+2y)²
=(5x-y)²

追问

谢谢

Answer 2

17. 9(x-y)²+12(x²-y²)+4(x+y)²=[3(x-y)]²+2×3×2(x+y)(x-y)+[2(x+y)]²
=[3(x-y)+2(x+y)]²=(5x-y)²;
19. x²+x-6=(x+3)(x-2);
20. x²-3x-4=(x-4)(x+1).

追问

您怎么知道19 20题的？

追答

你题目单里不是有吗？