Question

15. Află numărul natural x:
a) x + 2x + ... +20x = 1050
b) 6x + 12x + ... +192x =6336

Answer 1

a)x+2x+...+20x=1050

x(1+2+3+...+20)=1050

x*20*21/2=1050

x*10*21=1050

21x=105

x=105/21

x=5

b)6x+12x+...192x=6336

x(6+12+...+192)=6336

x(6(1+2+...+32))=6336

x(6*32*33/2)=6336

x(3*32*33)=6336

x*3168=6336

x=6336/3168

x=2