S.2數學題 幫幫手~!!

9^(x+2)=36
3^2(x+2) = 36
3^(2x+4) = 36
3^2x * 3^4 = 36
3^2x = 36 / (3^4)
(3^x)^2 = 4/9
3^x = √(4/9)
3^x = 2/3


2009-03-28 15:43:32 補充：
方法二 :

9^(x+2)=36

[3^(x+2)] ^ 2 = 6^2 (由於3^(x+2)不會是負數,下一步等式兩邊取正數)

3^(x+2) = 6

3^x * 3^2 = 6

3^x = 2/3

9^(x+2)=36
9^x+18=36
9^x=36-18
9^x=18
9^x/3=18/3
3^x=6

9x+18=36
9x=36-18
9x=18
x=2

3^(2)=6