Question

(x+1) + (x+2) + ......+ ( x+30) = 795

Answer 1

(x+1)+(x+2)+...+(x+30)=795

(x+x+x+...+x) + (1+2+3+...+30) = 795    

30x + 465 = 795   

30x = 795 - 465

30x = 330

x = 330 : 30

x = 11

Vậy x = 11

tho T-T

Answer 2

\((x+1)+(x+2)+...+(x+30)=795\\\Rightarrow (x+x+...+x)+(1+2+...+30)=795 (1)\)

Đặt \(A=1+2+...+30\)

Số các số hạng trong tổng \(A\) là:

\(\left(30-1\right):1+1=30\left(số\right)\)

Tổng \(A\) bằng:

\(\left(30+1\right)\cdot30:2=465\)

Thay \(A=465\) vào \(\left(1\right)\), ta được:

\(30x+465=795\\\Rightarrow 30x=795-465\\\Rightarrow 30x=330\\\Rightarrow x=330:30\\\Rightarrow x=11\)

#\(Toru\)

Answer 3

\(\left(x+1\right)+\left(x+2\right)+...+\left(x+30\right)=795\)

\(\Leftrightarrow30x+\left(1+2+...+30\right)=795\)

\(\Leftrightarrow30x+\dfrac{30\cdot31}{2}=795\)

\(\Leftrightarrow30x=795-\dfrac{30\cdot31}{2}=330\)

\(\Leftrightarrow x=\dfrac{330}{30}=11.\)