Answer:
-55
Step-by-step explanation:
the sqeuence seems to be subtracting by 2 everytime.
so it will be -1,-3,-5,-7,-9,-11,-13,-15,-17,-19,-21,-23,-25,-27,-29..
the answer will be 27*-2(-54) -1(because we start at -1 , not 0)
It is prime because nothing equals it other than 5x1
1+3+5+7+...+999 =
= 1+2+3+4+...+500
+1+2+3+...+499
= 2·(1+2+3+...+499) + 500
= 2·(499·500)/2 + 500
= 499·500 + 500
= 500·(499 + 1)
= 500·500
= 250.000
3 because 4×3=12 and if you divide12÷3/4 it helps you check
