Question 619372
a+1/(a^2-2a-3)- a+1/(a^2+4a+3)
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= a+1/(a-3)*(a+1) - a+1/(a+1)*(a+3)
= 1/(a-3) - 1/(a+3)
= ((a+3) - (a-3))/(a^2 - 9)
= 6/(a^2 - 9)