b) a+ 3/ a^2-1 - 1/ a^2 + a
Giải thích
b) a+3a2−1−1a2+a
=a+3a+1a−1−1aa+1
=aa+3aa+1a−1−a−1aa+1a−1
=a2+3a−a+1aa+1a−1
=a2+2a+1aa+1a−1
=a+12aa+1a−1=a+1aa−1.
b) a+3a2−1−1a2+a
=a+3a+1a−1−1aa+1
=aa+3aa+1a−1−a−1aa+1a−1
=a2+3a−a+1aa+1a−1
=a2+2a+1aa+1a−1
=a+12aa+1a−1=a+1aa−1.