解一元二次方程之十字相乘法专项练习题

1、 a2-7a+6=0：解一元二次方程十字相乘法专项练习j(2)8X2+6X-35=O：(3)18X2-21X+5=O；(4) 20 9y20y2=0：(5)2X2+3X+1=O：(6)2y2+y-6=0；(7)6X2-13X+6=O：(8)3a2-7a-6=0：(9)6x2-11x+3=0：(10)4m2+8m+3=0；(11)1OX2-21X+2=O：(12)8m2-22m+15=0：(13)4n2+4n-15=0：(14)6a2+a-35=0；(15)5x28x13=0：(16)4x2+15x+9=0：(17)15X2+X-2=O：(18)6y2+19y+10=0：(19) 2(a+b)

2、2+(a+b)(ab)6(a-b) 2=0：(20)7(X-1) 2+4(X-1)-20=0学乐教育数学(2)(2x+5)(4x-7) (4)-(4y-5)(5y+4) (6)(y+2)(2y-3) (8)(a-3)(3a+2) (10)(2m+1)(2m+3) (12)(2m-3)(4m-5) (14)(2a+5)(3a-7) (16)(X+3)(4x+3) (18)(2y+5)(3y+2) (2O)(X+1)(7X-17)参考答案： (1)(a-6)(a-1),(3)(3x-1)(6x-5), (X+1)(2X+1), (2x-3)(3x2), (9)(2x-3)(3x-1), (11)(

3、X-2)(1OX-1), (13)(2n+5)(2n-3), (15)(X+1)(5X-13), (17)(3x-1)(5x=2), (19)(3a-b)(5b-a),解一元二次方程十字相乘法专项练习题9.21一、十字相乘分解因式:理科不好就找乐普分解因式：x2 +3x + 2x2 3x + 2x2 + 2x 3x2 2x - 3x2 +5x + 6x2 5x + 6x2 +5x -6x2 5x 6x2 +x-2x2 -4x-12x2 + 2x 63x2 -8x +15x2 + 12x + 32x2 + lOx + 9x2 -3x-10x2 -2x-15分解因式：2x2 +5x + 22xz

4、-5x-3lx1 - 202x2 +5x-72xz +7x +32x2 7x + 63x2 +7x 62x2 -7x + 33x2 +8x 3lx1 7x + 63x2 -5x +25x2 -3x-25x2 +6x 86x2 -5x-256x2 7x + 3分解因式:) x3 -4x2 -21x31 - 10x2 + 3xx4 _6x2 -27x4 _10x2 +9(2x - 3-+ 3(2x -3) + 2(x2 + 8xf+ 22(x2 + 8x) + 120二、用因式分解法解下列方程(1) a2-7a+6=0；(2)8x2+6x-35=0；(3)18x2-21x+5=0：(5)2x2+3

5、x+1=0；(4) 209y20y2=0； (6)2y2+y-6=0；(7)6x2-13x+6=0；(8)3a2-7a-6=0；(9)6x2-11x+3=0；(10)4m2+8m+3=0；(11)10x2-21x+2=0；(12)8m2-22m+15=0；(14)6a2+a-35=0；(13)4n2+4n 15=0；(16)4x2+15x+9=0：(15)5x28x7 3=0；(17)15x2+x-2=0；(18)6y2+19y+10=0；(20)7(x-1) 2+4(x-1)(19) 2(a+b) 2+(a+b)(a-b)-6(a-b) 2=0：-20=0答案：十字相乘分解因式： 分解因式：

6、x2 3x + 2 = (x - 2)(x D x2 2x - 3 = (x - 3)( x + 1) x2 5x + 6 = (x - 3)( x 2) x2 - 5x 6 = (x - 6)(x + 1) x2 - 4x - 12 = (x - 6)(x + 2) x2 8x + 15 = (x - 3)( x 5) x2 + lOx + 9 = (x + 9)( x + 1) x2 -2x -15 = (x - 5)(x + 3) 分解因式：2x2 + 5x + 2 = (2x + 1)(x + 2) lx1 - 3x - 20 = (2x + 5)( x - 4) 2x2 + 7x +

7、 3 = (2x + 1)( x + 3) 2x2 - 7x + 6 = (2x - 3)(x - 2) 3x2 + 7x 6 = (3x 2X* + 3) 3x2 5x + 2 = (3x 2)( x 1) 5x2 + 6x 8 = (5x - 4)( x + 2) 6x2 -llx + 3 = (2x - 3X3x - 1)x2 + 2x - 3 = (x + 3)( x 1) x2 + 5x + 6 = (x + 2)( x + 3) x2 + 5x 6 = (x + 6)(x - 1) x2 + x - 2 = (x + 2)(x - 1) x2 + 2x - 63 = (x + 9)

8、(x - 7) x2 + 12x + 32 = (x + 8)( x + 4) x2 - 3x - 10 = (x - 5)(x + 2)lx1 5x 3 = (2x + l)(x 3) 2x2 + 5x - 7 = (2x + 7)(x 1)2 7x + 3 = (2x 1)( x 3)2x2 - x -6 = (2x - 3)(* + 2)3x2 + 8x 3 = (3x - IX* + 3)5x2 3x - 2 = (5x + 2)( x 1)6x2 5x 25 = (2x 5)(3x + 5)分解因式:.x2 + x-(fz2 -«1= (x+ a)x-(a - 1)、 八3

9、x " - 10x2 +3x = x(3x - 1)(x - 3) x4 - 6x2 -27 = (x - 3)(x + 3)(x2 + 3) x4 - 10x2 + 9 = (x + 3)(x - 3)(x + l)(x - 1)lx - 3)2 + 3(2x -3) + 2 = 2(x- l)(2x - 1)(x2 + 8x)2 + 22( x2 + 8x) + 120 = (x2 +8x + 10)( x + 2)( x + 6)x' - 4x2 - 2lx = x(x _J)(x + 3)参考答案:(a-6)(a-1), (3)(3x-1)(6x-5), (5)(x+1)(2x+1), (7)(2x-3)(3x-2), (9)(2X-3)(3X-1), (11)(X-2)(1OX-1), (13)(2n+5)(2n-3), (15)(x+1)(5x-13), (17)(3x-1)(5x=2), (19)(3a-b)(5b-a),(2x+5)(4x-7