用换底公式计算.
log(abc)X = 1/[log(X)abc] = 1/[log(X)a + log(X)b + log(X)c] = 1/[1/log(a)X + 1/log(b)X + 1/log(c)X] = 1/[1/1 + 1/(1/2) + 1/(1/4)] = 1/7
用换底公式计算.
log(abc)X = 1/[log(X)abc] = 1/[log(X)a + log(X)b + log(X)c] = 1/[1/log(a)X + 1/log(b)X + 1/log(c)X] = 1/[1/1 + 1/(1/2) + 1/(1/4)] = 1/7