已知:27^2=a^6=9^b,求(a-1/5b)^2+(a+1/5b)^2+2b(a-1/25)的值.
问题描述:
已知:27^2=a^6=9^b,求(a-1/5b)^2+(a+1/5b)^2+2b(a-1/25)的值.
答
27^2=(3^3)^2=3^6=a^6
所以a=3
9^b=(3^2)^b=3^2b=27^2=3^6
所以2b=6
b=3
(a-1/5b)^2+(a+1/5b)^2+2b(a-1/25b)的值
=a^2-2/5ab+b^2/25+a^2+2/5ab+b^2/25+2ab-2/25b^2
=2a^2+2ab
=2a(a+b)
=2*3*[3+3]
=36
答
会做但用电脑不知道咋么写啊
答
已知:27^2=a^6=9^b
因为(3^3)^2=3^6=a^6,所以a=3
因为27^2=9*3*9*3=9^3=9^b,所以b=3
(a-1/5b)^2+(a+1/5b)^2+2b(a-1/25)
=(12/5)^2+(18/5)^2+6*(74/25)
=144/25+324/25+444/25
=912/25