Question

Someone please help me out!

Answer 1

try it with a couple different numbers

try 4: 1^2 +2^2 +3^2 +4^2 = 1 +4 +9 +16 =30

formula: 4(4+1)(2*4+1)/6 = 4*5*9 = 180/6=30

this one works

now try 5

1^2 + 2^2+3^2+4^2+5^2 = 55

formula: 5(5+1)(2*5+1)/6 = 5*6*11 = 330/6=55

I tried a larger number ( 14) as well and it worked

so you can say that this is true