Answer: F
Step-by-step explanation:
1+2+...+n = n*(n+1)/2 for all natural numbers n.
Left-hand-side = (5+1)+(5+2)+...+(5+10)=5*10+10*(10+1)/2=50+55=105
Right-hand-side = (4)+(4+1)+...+(4+9)=4*10+9*(9+1)/2=40+45=85
105≠85
The equation is false
