Question

Rezolvati ecuatiile:
a) x+2x+3x+…+20x=420
b) (x-1)+(x-2)+(x-3)+…+(x-20)=0

Answer 1

Răspuns:

Explicație pas cu pas:

a) x + 2x + 3x + … + 20x = 420

x*(1 + 2 + 3 + ... + 20) = 420

x*20*21/2 = 420

x*210 = 420

x = 420 : 210 = 2

b) (x - 1) + (x - 2) + (x - 3) + … + (x - 20) = 0

20x - (1 + 2 + 3 + ... + 20) = 0

20x - 210 = 0

20x = 210

x = 210/20 = 21/2 = 10,5