Question

a, (x+1) + (x+2) + (x+3) +....+ (x+9)=90

Timf x

Answer 1

\(\left(x+1\right)+\left(x+2\right)+...+\left(x+9\right)=90\)

Ta có 9 SSH (từ 1 đến 9)

9.x+(1+2+3+...+9)=90

9x+(9+1).9:2=90

9x+45=90

9x=90-45=45

x=45:9

x=5

Answer 2

(x+1)+(x+2)+...+(x+9)=90

Ta có 9 SSH (từ 1 đến 9)

9.x+(1+2+3+...+9)=90

9x+(9+1).9:2=90

9x+45=90

9x=90-45=45

x=45:9

x=5

Answer 3

\(\left(x+1\right)+\left(x+2\right)+\left(x+3\right)+...+\left(x+9\right)=90\)

\(\Rightarrow\left(x+x+x+...+x\right)+\left(1+2+3+...+9\right)=90\)

\(\Rightarrow9x+45=90\)

\(\Rightarrow9x=90-45\)

\(\Rightarrow9x=45\Rightarrow x=5\)

Answer 4

Ta có:

    ( x + 1 ) + ( x + 2 ) + ( x + 3 ) +...+ ( x + 9 ) = 90

=> x + 1 + x + 2 + x + 3 + ... + x + 9 = 90

=> 9x + ( 1 + 2 + 3 +...+ 9 ) = 90

=> 9x = 90 - 45 = 45

=> x = 45 : 9 = 5