GWD 3-6

davidsfo

Q6:

If x and k are integers and (12^x)(4^2x+1) = (2^k)(3²), what is the value of k?

 

A.    5

B.     7

C.     10

D.    12

E.     14

我不明白怎么做这道题。答案是E

thanks

mandyuuqq

(12^x)(4^2x+1) = (2^k)(3²)即4^x3^x4^2x4=(2^k)(3²),即2^2x+4x+23^x=(2^k)(3²)

再比较一下等式两边可以得出：x=2; 6x+2=k, 所以答案是k=14

davidsfo

thanks.我忘了 12^x = (3^x) (4^X)

感激