Answer:
xn = n·(n + 1)/2
Step-by-step explanation:
Answer:
None
Step-by-step explanation:
There is no integer equivalent to 91/2, integers can't have a decimal.
However, I assume you would like me to answer 9.5, even though it isn't an integer.
Answer:

will give you an explanation if you want tag me on comment.
4a^4 -2b^2 +40
a=2
b=7
4(2)^4 -2(7)^2 +40
PEMDAS is what your gonna use to solve this you go from right to left
First is P which is parentheses which is none
second is E which stands for exponents
4(32)-2(49)+40
now MD multiply or divide
128-98+40
now add or subtract
30+40
last one
70 this is your answer i hope