Question

x+2×x+3×x +...+10×x =550

Answer 1

x + 2 . x + 3 . x +....+ 100.x = 550

⇔ x.(1 + 2 + 3 + ....+ 100) = 550

Ta có : 

1 + 2 + 3 + ....+100 = \(\frac{\left(100+1\right).100}{2}\)= 5050

\(\Rightarrow\)x . 5050 = 550

\(\Rightarrow\)x = 550 : 5050

\(\Rightarrow\)x = \(\frac{11}{101}\)

Answer 2

a) 90 b) 80 c) 50 d) 10

Answer 3

Mình nhầm a) 10 b) 100 c) 55 d) 11