◆◇◆(X-2Y)(3X-7Y)^2+4(Y-2X)(X+Y)^2 如何分解因式?还有 a^2+4b^2+9c^2-4ab-12bc+6ac怎么分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分
问题描述：
◆◇◆(X-2Y)(3X-7Y)^2+4(Y-2X)(X+Y)^2 如何分解因式?
还有 a^2+4b^2+9c^2-4ab-12bc+6ac
怎么分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分分
答
原式=（X-2Y）（3X-7Y+2X+2Y）（3X-7Y-2X-2Y）
=5（X-2Y）（X-Y）（X-9Y）