已知a的m次方=5,a的2n次方=7,求a的3m-4n次方的值.

问题描述:

已知a的m次方=5,a的2n次方=7,求a的3m-4n次方的值.

a^(3m-4n)
=a^3m/a^4n
=(a^m)^3/(a^2n)^2
=5^3/7^2
=125/49


a^m=5,a^2n=7
∴a^(3m-4n)
=a^3m÷a^4n
=(a^m)³÷(a^2n)²
=5³÷7²
=125/49