用十字相乘乘法因式分解 2x²+7x+3 x²-3xy+2x²y

用十字相乘乘法因式分解 2x²+7x+3 x²-3xy+2x²y
用十字相乘乘法因式分解 2x²+7x+3 x²-3xy+2x²y

用十字相乘乘法因式分解 2x²+7x+3 x²-3xy+2x²y
2x²+7x+3
=2x²+6x+x+3
=2x(x+3)+(x+3)
=(x+3)(2x+1)
x²-3xy+2y²
=x²-2xy-xy+2y²
=x(x-2y)-y(x-2y)
=(x-2y)(x-y)

2x²+7x+3
2 1
1 3
______
6+ 1=7

2x²+7x+3=(2x+1)(x+3)


x²-3xy+2y²
1 -2
1 -1
_________
-2+(-1)=-3

x²-3xy+2y²=(x-2)(x-1)