你是想求x的m+1次方、x的3+n次方、x的m+n+1次方的乘积吧?
x^(m+1)×x^(3+n)×x^(m+n+1)=x^(2m+2n+5)=x^(2m+2n)×x^5=[x^(m+n)]²×x^5=160x^5
好像还少一个条件!
x^m=8,
m*lgx=lg8,(1)
x^n=5,
n*lgx=lg5,(2)
(1)+(2),
(m+n)*lgx=lg8+lg5=lg40,
lgx=lg40/(m+n)=lg[40^(1/(m+n)],
x=40^[1/(m+n)],
x^(m+1)=x^m*x=8*40^(1/(m+n)],
x^(n+3)=x^n*x^3=5*40^[3/(m+n)],
x^(m+n+1)=(x^m)*(x^n)*x=8*5*40^[1/(m+n)]=40^[(m+n+1)/(m+n)].