Question

已知9n+1-32n=72，求n的值。

Answer 1

解：∵9n+1-32n=9n+1-9n=9n（9-1）=9n×8，而72=9×8，
∴当9n+1-32n=72时，9n×8=9×8，
∴9n=9，
∴n=1．

Answer 2

9^n＋1－3²ⁿ＝72    

(3²)ⁿ×9－3²ⁿ＝72   

3²ⁿ×9-3²ⁿ＝72 

3²ⁿ×(9-1)＝72 

3²ⁿ×8＝72 

3²ⁿ＝ 3²      

2n=2

n=1                                                                                                                    

Answer 3

n=71/23

Answer 4

9n+1-32n=72
23n=-71
n=-71/23

Answer 5

23n=71
n=71/23