Question

课外习题：因式分解（十字相乘法）

2x^3+6x^2+4x
x^4-6x^2+8
x^4-13x^2+36
(x-2y)^2-2(x-2y)-24
7x^2-2xy-5y^2

Answer 1

2x^3+6x^2+4x=x(2x+2)(x+2)
x^4-6x^2+8 =(x^2-2)(x^2-4)
x^4-13x^2+36 =(x^2-4)(x^2-9)
(x-2y)^2-2(x-2y)-24 = (x-2y+4)(x-2y-6)
7x^2-2xy-5y^2 ==(7x+5y)(x-y)

Answer 2

2x^3+6x^2+4x =(2x+1)(x+4)
x^4-6x^2+8 =(x-2)(x-4)
x^4-13x^2+36 =(x-4)(x-9)
(x-2y)^2-2(x-2y)-24 =(x-2y-6)(x-2y+4)
7x^2-2xy-5y^2=(7x+5y)(x-y)