Question

找规律:1乘(1+2)=3 (1+2)乘(1+2)=9 (1+2+?)乘(1+2)=?(1+2+?)乘(1+2+3)=?

Answer 1

1*3=3,3*3=0

(3+x)*3=y (1)

(3+x)*6=y^2 (2)

(2)/(1) y=2,

代入(1) x=2/3 - 3 = -7/3