因式分解:(1)3x^2+7x+2 (2)5x^2+13x-6=0 (3)6x^2+13x-15=0

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因式分解:(1)3x^2+7x+2  (2)5x^2+13x-6=0  (3)6x^2+13x-15=0

因式分解:(1)3x^2+7x+2 (2)5x^2+13x-6=0 (3)6x^2+13x-15=0
因式分解:(1)3x^2+7x+2 (2)5x^2+13x-6=0 (3)6x^2+13x-15=0

因式分解:(1)3x^2+7x+2 (2)5x^2+13x-6=0 (3)6x^2+13x-15=0
(1)3x^2+7x+2
=3x^2+6x+x+2
=3x(x+2)+(x+2)
=(x+2)(3x+1)
(2)5x^2+13x-6=0
5x^2-2x+15x-6=0
x(5x-2)+3(5x-2)=0
(5x-2)(x+3)=0
x=2/5,x=-3
(3)6x^2+13x-15=0
6x^2+18x-5x-15=0
6x(x+3)-5(x+3)=0
(x+3)(6x-5)=0
x=-3,x=5/6

(1)(3x+1)(x+2)
(2)(5x-2)(x+3)=0
(3)(6x-5)(x+3)=0

(1) 3x^2+7x+2=(3x+1)(x+2)
(2) 5x^2+13x-6=(5x-2)(x+3)
(3) 6x^2+13x-15=(6x-5)(x+3)

1).=(3x+1)(x+2)
2).=(5x-2)(x+3)
3).=(6x-5)(x+3)