因式分解:(1)x^2+8x+15; (2)t^2-7t+6; (3)x^2+2x-15; (4)a^2-4a-21

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因式分解:(1)x^2+8x+15;(2)t^2-7t+6;(3)x^2+2x-15;(4)a^2-4a-21因式分解:(1)x^2+8x+15;(2)t^2-7t+6;(3)x^2+2x-15;(4

因式分解:(1)x^2+8x+15; (2)t^2-7t+6; (3)x^2+2x-15; (4)a^2-4a-21
因式分解:(1)x^2+8x+15; (2)t^2-7t+6; (3)x^2+2x-15; (4)a^2-4a-21

因式分解:(1)x^2+8x+15; (2)t^2-7t+6; (3)x^2+2x-15; (4)a^2-4a-21
1)x^2+8x+15=(x+3)(x+5)
(2)t^2-7t+6=(t-1)(t-5)
; (3)x^2+2x-15=(x-3)(x+5)
; (4)a^2-4a-21=(x-7)(x+3)

(1) (x+3)(x+5)
(2) (t-1)(t-6)
(3) (a-7)(a+3)
这个东西多做吧,做多了就熟悉了

1) (x+3)(x+5)
2) (2t-3)(t-2)
3) (x+5)(x-3)
4) (x+3)(x-7)