30-x is a power of 3. How many powers of 3 are less than 30? there are 3^1, 3^2, 3^3. we immediately see that the answer is 3^3=27 because 27+3=30. we also immediately see that this is the only solution because exponential of x and x do not have the same growth rate, so if x=3 is a solution this solution is unique.
![“อ.เบียร์ คนตื่นธรรม” มาตามคำเรียกร้อง แหกศาสตร์ฮวงจุ้ย เตือนสติอย่างมงาย | แฉ 7 พ.ย. 67 [1/3]](http://i.ytimg.com/vi/5fc4S3xBNfc/mqdefault.jpg)
![[LIVE] : ONE ลุมพินี 86 | คู่เอก "คมเพชร vs ชาติพยัคฆ์"](http://i.ytimg.com/vi/m3q_dRYDuU8/mqdefault.jpg)
thats tricky
30-x is a power of 3.
How many powers of 3 are less than 30?
there are 3^1, 3^2, 3^3.
we immediately see that the answer is 3^3=27 because 27+3=30.
we also immediately see that this is the only solution because exponential of x and x do not have the same growth rate, so if x=3 is a solution this solution is unique.