- 余辉
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3x+5/(x+1)(x+2)
= (3x+6)/((x+1)(x+2)) - 1/((x+1)(x+2))
= 3/(x+1) - ((x+2) - (x+1))/((x+1)(x+2))
= 3/(x+1) - 1/(x+1) + 1/(x+2)
= 2/(x+1) + 1/(x+2)
3x+5/(x+1)(x+2)
= (3x+6)/((x+1)(x+2)) - 1/((x+1)(x+2))
= 3/(x+1) - ((x+2) - (x+1))/((x+1)(x+2))
= 3/(x+1) - 1/(x+1) + 1/(x+2)
= 2/(x+1) + 1/(x+2)