Question

tìm x biết:

(x+1)+(x+2)+...+(x+20)=40470

Answer 1

(x+1)+(x+2)+...+(x+20)=40470

x+x+x+...+x(20 chữ số x) +1+2+3+...+20=40470

20x+210=40470

20x=40470-210

20x=40260

x=40260:20

x=2013

Answer 2

(x+x+...+x)+ (1+2+3+...+20)= 40470

20*x + 210 = 40470

20* x = 40470-210=40260

x = 40260 / 20

x= 2013