2 câu trả lời
`(1+2+3+....+50)x=2+4+6+....+100`
`<=>(1+2+3+....+50)x=2626`
`<=>1275x=2550`
`<=>x=2`
Vậy `x=2`
`(1 +2 +3 +...+50).x = 2 +4 +6 +100`
`⇒ [50.(50 +1)]/2.x = [50.(100 +2)]/2`
`⇒ 1275.x = 2550`
`⇒ x = 2550 : 1275`
`⇒ x = 2`
`Vậy` `x = 2`