数学题目因式分解

5x²-14xy+9y²
= 5x²-5xy - 9xy+9y²
= 5x(x-y) -9y(x-y)
= (5x - 9y)(x-y)

或者直接用十字相乘法

公式法计算
∵5x²－14xy＋9y²＝0时x＝9y/5，或x＝y
∴5x²－14xy＋9y²＝（5x－9y）（x－y）

十字相乘法
5x -9y
1x -1y
5x*(-1y)+(-9y)*(1x)=-14xy
(5x-9y)(x-y)

5x²-14xy+9y²
=x²+y²-2xy+4x²-8xy+4y²+4y²-4xy
=(x-y)²+4(x-y)²+4y(y-x)
=5(x-y)²-4y(x-y)
=(x-y)[5(x-y)-4y]
=(x-y)(5x-9y)