This differs on what number you want to talk about. 1 is the hundreds, 8 is the tenths, 7 is the ones.
Answer:

Step-by-step explanation:
Given


Required
Determine the formula
An exponential function is of the form:

For point 




For point 

Substitute 7 for a

Divide both sides by 7

Take 4th root of both sides
![\sqrt[4]{81} =\sqrt[4]{b^4}](https://tex.z-dn.net/?f=%5Csqrt%5B4%5D%7B81%7D%20%3D%5Csqrt%5B4%5D%7Bb%5E4%7D)
![\sqrt[4]{81} =b](https://tex.z-dn.net/?f=%5Csqrt%5B4%5D%7B81%7D%20%3Db)
![b = \sqrt[4]{81}](https://tex.z-dn.net/?f=b%20%3D%20%5Csqrt%5B4%5D%7B81%7D)

Substitute 7 for a and 3 for b in 


<u> b</u> = 1.5
-3
Cross Multiply
b = - 3 * ( 1.5 )
b = - 4.5
Answer:
-42 ≤ x ≤ 102
Step-by-step explanation:
Compound from the fact that we're combining x≤42 and x≤102.
10x^2-10x+20 is the answer to this