User:Scientist nick

In this question, there is two answers.

(question) what is x?      1, 2, 3, x

(answer) x=4,10

(explanation) 1.$$(1+0=1), (1+1=2), (1+2=3), (1+3=4)$$

2.$$ (n-1)*(n-2)*(n-3)+n  (n=1~4)  $$

(1-1)*(1-2)*(1-3)+1=0*(-1)*(-2)+1=1 (2-1)*(2-2)*(2-3)+2=1*0*(-1)+2=2 (3-1)*(3-2)*(3-3)+3=2*1*0+3=3 (4-1)*(4-2)*(4-3)+4=3*2*1+4=10

x=10, 4