Answer:
-7240
Explanation:
The nth term is -10n + 24.
So the combination of the first and second term would be (-10+24)+(-10x2+24) and this would continue for the first 40 terms so the 24s would add up to 24x40=960. Meanwhile, the -10s would keep adding up so it would be -10-20-30-40.... which you can simplify by making it -10(1+2+3+4) all the way to 40 to make the calculation easier... u can further simplify by making 41 = one pair of numbers so 40+1, 39+2 until you get 21+20 so ur left with -10(20 pairs of 41) so -10(20x41) = -10(820)= -8200.
Add this to your initial 960 so
-8200 +960 = -7240
Hope this helps