tolong jawab yh banjir point,,jangan asal asalan

a.
= 1 +3 +5 +7 +9
=99 +97 +95 +93 +91
=100+100+100+100+100
=100×50÷2=250
b.
= 1-2 +3-4 +5-6 +7-8 +.... -100
= (1-2) + (3-4) + (5-6) + (7-8) +.... (99-100)
= -1 + -1 + -1 + -1 +.... -1
= -1×50= -50
c.
bilangan negatif:
= -100-99-98....-2-1
= -1 -2 -3 ....-99-100
= -101 -101-101...-101-101
= -101×50÷2= -5050
bilangan positif:
= 1 + 2 + 3 +4.... +50
=50+49 +48 +47... +1
=51 +51 +51 +51... +51
=51×50÷2=1275
Bilangan negatif+Bilangan positif
= -5050 + 1.275
= -3775