Answer:
Step-by-step explanation:
The current function of time is defined as follows:
where 
is the charge function.
For the given charge function of time 
we have the following current function:
In the problem it is proposed that 
.
Examining the expression of 
we obtained by deriving with the expression proposed by the problem and comparing term by term:
We conclude that 
and 
.
That's the "decimal point".
Answer:
Now, Mr Lee's age is 40 years, his son's age is 13 years.
Step-by-step explanation:
<u>4 years ago:</u>
Son's age = x years
Mr. Lee age = 4x years
<u>Now:</u>
Son's age = x + 4 years
Mr. Lee age = 4x + 4 years
The sum of the ages of Mr Lee and his son is 53 now, so
Now, Mr Lee's age is 40 years, his son's age is 13 years.
Need a LOT more information and a graphic would help.
