映射f的对应法则
x | 1 | 2 | 3 | 4 |
f(x) | 3 | 4 | 2 | 1 |
映射g的对应法则
x | 1 | 2 | 3 | 4 |
g(x) | 4 | 3 | 1 | 2 |
则f[g(1)]的值为( )