\(\left(x+1\right)\cdot\left(x+2\right)\cdot\left(x+3\right)\cdot...\cdot\left(x+20\right)=240\)
\(\left(x+x+x+...+x\right)\cdot\left(1+2+3+...+20\right)=240\)
\(20x\cdot210=240\)
\(20x=\frac{240}{210}=\frac{8}{7}\)
\(\Rightarrow x=\frac{8}{7}\div20=\frac{2}{35}\)
(x+1)(x+2)(x+3)....(x+20)=240
=> x(1+2+3+...+20) = 240
=> x.210=240
x = 240:210
x=8/7
( x+1 ) . ( x+2 ) . ... . ( x+20 ) = 240
( x+x+...+x ) . ( 1+2+3+...+20 ) = 240
Số số hạng là :
( 20 - 1 ) : 1 + 1 = 20 ( số )
Tổng là :
( 20 + 1 ) . 20 : 2 = 210
Ta có :
20x . 210 = 240
20x = 240 : 210
20x = \(\frac{8}{7}\)
x = \(\frac{8}{7}:20\)
x = \(\frac{2}{35}\)
~ Chúc học tốt ~
làm lại :
(x+1)(x+2)(x+3)....(x+20)=240
=>(x+x+x+...+x).(1+2+3+...+20)=240
=> 20x.210=240
20x=240:210
20x=8/7
x=8/7:20
x=2/35
