Question

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

 

 

Answer 1

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

x*9+(1+2+3+4+5+6+7+8+9)=90

x*9+45=90

x*9=90-45

x*9=45

x=45:9

x=5

~Hok Tốt~

K nhé MN????

Answer 2

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

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

\(\Rightarrow\) \(x.45=90\)

\(\Rightarrow\) \(x=2\)

Answer 3

X + 2X + 3X +...+ 9X = 90

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

          45 x X = 90

                  X = 90 : 45

                  X = 2