23. the nth term of a sequence is n2 + 3. find the first 3 terms of this sequence.

24. work out the difference between the 5th and 10th terms of the sequence in q23

23.
assuming you mean

first term is n=1, so 1²+3=1+3=4
2nd is n=2 so 2²+3=4+3=7
3rd is n=3 so 3²+3=9+3=12

the first 3 terms are 4,7,12

24.
5th term is 5²+3=25+3=28
10th term is 10²+3=100+3=103

difference is 103-28=75

No a triangle cannot be formed because when you add the two smallest number together (which would be 11) the have to be bigger than the number it is "against" ( which would be 12)