十字相乘法分解因式的练习题
十字相乘法分解因式
班级________姓名_________
一、选择题
1.如果x 2-px +q =(x +a )(x +b ) ,那么p 等于 ( )
A .ab B .a +b C .-ab D .-(a +b )
2.如果x 2+(a +b ) ⋅x +5b =x 2-x -30,则b 为 ( )
A .5 B .-6 C .-5 D .6
3.多项式x -3x +a 可分解为(x -5)(x -b ) ,则a ,b 的值分别为 ( )
A .10和-2 B .-10和2 C .10和2 D .-10和-2
4.不能用十字相乘法分解的是 ( )
A x +x -2 B 3x -10x +3x C 4x +x +2 D 5x 2-6xy -8y 2
5.将下述多项式分解后,有相同因式x -1的多项式有 ( )
①x -7x +6; ②3x +2x -1; ③x +5x -6;
④4x -5x -9; ⑤15x -23x +8; ⑥x +11x -12
A .2个 B .3个 C .4个 D .5个
二、填空题
7.x +3x -10=__________.
8.m -5m -6=(m +a )(m +b ) . a =__________,b =__________.
9.2x -5x -3=(x -3)(__________).
210.x +________-2y =(x -y )(__________). [**************]2
11.若x -y =6,xy =173223,则代数式x y -2x y +xy 的值为__________. 36
三、12.把下列各式分解因式:
22(1)x -2x -15 (2)x -5xy +6y 2
(3)2x -5x -3; (4)3x +8x -3
32(5)x -10x +9 (6)7(x +y ) -5(x +y ) -2(x +y ) ; 4222
13. 因式分解
(1)2x 2+15x +7 (2)3a 2-8a +4 (3) 5x 2+7x -6
(4) 6y 2-11y -10 (5) 5a 2b 2+23ab -10
(6) 3a 2b 2-17abxy +10x 2y 2 (7) x 2-7xy +12y 2
(8) x 4+7x 2-18 (9) 4m 2+8mn +3n 2
(10) 5x 5-15x 3y -20xy 2 (11)x -7x +6; (12)x -5x -36;
(13)4x 4-65x 2y 2+16y 4 (14)a -7a b -8b
(15)6a -5a -4a ; (16)4a -37a b +9a b .
14.把下列各式分解因式:
(1)(x -3) -4x ; (2)x (x -2) -9;
(3)(3x +2x +1) -(2x +3x +3) ; (4)(x +x ) -17(x +x ) +60;
(5)(x +2x ) -7(x +2x ) -8; (6)(2a +b ) -14(2a +b ) +48. [***********][1**********]242