x的2m次方=3,求(3x的3m次方)的2次方-4(x的平方)的2m次方

题目

x的2m次方=3,求(3x的3m次方)的2次方-4(x的平方)的2m次方

答案

[3x^(3m)]^2-4(x^2)^(2m)
=9x^(6m)-4x^(4m)
=9*[x^(2m)]^3-4*[x^(2m)]^2
=9*3^3-4*3^2
=9*27-4*9
=261-36
=225