Question

这一题怎么计答案。求过程???

Answer 1

原式=12/[(m+3)(m-3)]一[2x(m十3)]/[(m十3)(m一3)]
=[一2(m一3)]/[(m十3)(m一3)]
=-2/(m十3)

Answer 2

因为分母不能为零，所以m不等于正负3
通分变为12/(m^2-9)-(2m+6)/(m^2-9)
相减得到=(-2m+6)/(m^2-9)
分子分母提取公因式得到：=-2(m-3)/(m-3)(m+3)

约分：得到答案：=-2/(m+3) （m不等于正负3）

Answer 3

12/(m^2-9)分母为m^2-9，显然m^2-9≠0，m≠±3
12/(m^2-9)-2/(m-3)
=12/(m^2-9)-2(m+3)/（m^2-9)
=(12-2m-6)/（m^2-9)
=(6-2m)/（m^2-9)
=-2/(m+3)

Answer 4

先通分，m-3乘以m+3，得到m2-9，2 乘以m+3，再相减，这时m不等于+3与-3

Answer 5

12/(m^2-9)-2/(m-3)
=12/(m^2-9)-2(m+3)/(m-3)(m+3)
=(12-2m-6)/(m-3)(m+3)
=-2(m-3)/(m-3)(m+3)
=-2/(m+3)