Answer:
n(n+1)(n+5)/3
Step-by-step explanation:
there is no value, as we don't know n.
but we can create a summary formula/ function definition :
this is the sum for k = 1 to n of k×(k+3)
k×(k+3) = k² + 3k
so, the overall sum splits into the sum of k² for k=1 to n, and the sum of 3k for k=1 to n.
and the sum of 3k is 3 times the sum of k for k=1 to n.
Σk² for k=1 to n = [n(n+1)(2n+1)]/6
Σk for k=1 to n = n(n+1)/2
3×Σk for k=1 to n = 3×n(n+1)/2
so, we have a function formula
n(n+1)(2n+1)/6 + 3n(n+1)/2 = n(n+1)(2n+1)/6 + 9n(n+1)/6 =
= n(n+1)(2n+1+9)/6 = n(n+1)(2n+10)/6 = n(n+1)(n+5)/3
Answer:
1215 minutes are the possible numbers he has used his phone in a month.
Step-by-step explanation:
He has a monthly fee of 14$ then to the least that he has been charged we need to substract the monthly fee as follows:
Monthly charged = 74,75-14
Monthly charged= 60,75$
Then he pays an additional 0,05 $/minute of use, to know the consume:
Minutes= 
Minutes= 1215 possible numbers of minutes he has used his phone.
One litre because 1 litre=1000ml
so i litre is better
Answer:

Step-by-step explanation:
Given

Required
Rewrite in logarithmic form
We start by taking log of both sides


From laws of logarithm;

So;
becomes

Divide both sided by log3


From laws of logarithm;

So;
becomes


Hence,
in logarithm form is 