1、若3^a=5,9^b=10,求3^a+2b的值2、若n是正整数,a^2n=2,求（2a^3n）^2-3(a^2)^2n的值3、已知（3x-y)^2n=1/10,(3x+y)^n=5求[(3x+y)(3x-y)]^4n的值

Question

1、若3^a=5,9^b=10,求3^a+2b的值
2、若n是正整数,a^2n=2,求（2a^3n）^2-3(a^2)^2n的值
3、已知（3x-y)^2n=1/10,(3x+y)^n=5
求[(3x+y)(3x-y)]^4n的值

Answer 1

1、3^a=5,9^b=10,
(3^2)^b=10
3^2b=10
3^(a+2b)=3^a*3^2b=5*10=50
2、a^2n=2,
（2a^3n）^2-3(a^2)^2n
=4a^6n-3a^4n
=4(a^2n)^3-3(a^2n)^2
=4*2^3-3*2^2
=32-12
=20
（3x-y)^2n=1/10,(3x+y)^n=5
[(3x+y)(3x-y)]^4n
=(3x+y)^4n*(3x-y)^4n
=[(3x+y)^n]^4*[（3x-y)^2n]^2
=5^4*(1/10)^2
=(25/10)^2
=(5/2)^2
=25/4