Question

Tìm x biết

(x-1)+(x-2)+(x-3)+...+(x-19)+(x-20)=-619

Answer 1

\(\Rightarrow20x-\left(1+2+....+20\right)=-619\)

Tự làm tiếp

Answer 2

Ta có : x - 1 + x - 2 + x - 3 + ...+ x - 19 + x - 20 = - 619

(x + x +x + ...+ x ) + ( - 1 - 2 - 3 - ...- 20) = - 619

20x + (-210) = -619

20x = -619 + 210

20x = - 409

x = -20,45

Answer 3

-20