用十字相乘法完成下面各题4x²+11x+6 3x²+10x+8 6x²-7xy-5y² 4(a+b)²+4(a+b)-1
1个回答

4x 3

*

x 2

所以 4x²+11x+6 = (4x + 3)(x + 2)

3x 4

*

x 2

所以,3x²+10x+8 = (3x + 4)(x + 2)

3x -5y

*

2x y

所以,6x²-7xy-5y² = (3x - 5y)(2x + y)

2(a + b) -3

*

2(a + b) 5

所以 4(a+b)²+4(a+b)-15 = [(a + b) -3 ] [ (a + b) + 5] = (a + b - 3)(a + b + 5)