Ta có: \(\dfrac{x}{4}+\dfrac{x}{5}=\dfrac{18}{10}\\ < =>\dfrac{2,5x}{10}+\dfrac{2x}{10}=\dfrac{18}{10}\\ < =>2,5x+2x=18\\ < =>4,5x=18\\ =>x=\dfrac{18}{4,5}=4\)
Mình ghi lại cho dễ nhìn:
Theo đề bài ta có:
\(\dfrac{x}{4}+\dfrac{x}{5}=\dfrac{x5}{4.5}+\dfrac{x4}{5.4}=\dfrac{x5+x4}{20}=\dfrac{9x}{20}=\dfrac{18}{10}\)
Mà \(\dfrac{9x}{20}=\dfrac{18}{10}=\dfrac{36}{20}\) nên:
9x = 36 => x = 36 : 9 =4
Vậy x = 4.
Theo đề bài ta có:
\(\dfrac{x}{4}+\dfrac{x}{5}=\dfrac{x5}{4.5}+\dfrac{x4}{5.4}=\dfrac{x5+x4}{20}=\dfrac{9x}{20}=\dfrac{18}{10}\)
Mà \(\dfrac{9x}{20}=\dfrac{18}{10}=\dfrac{36}{10}\) nên:
9x = 36 => x = 36 : 9 = 4
Vậy x = 4.
Sửa lại:
Theo đề bài ta có:
x4+x5=x54.5+x45.4=x5+x420=9x20=1810" id="MathJax-Element-20-Frame" role="presentation" style="border:0px; box-sizing:border-box; direction:ltr; display:inline-block; float:none; font-size:18.06px; line-height:0; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; padding:1px 0px; position:relative; white-space:nowrap; word-spacing:normal; word-wrap:normal" tabindex="0">
9x20=1810=3610" id="MathJax-Element-21-Frame" role="presentation" style="border:0px; box-sizing:border-box; direction:ltr; display:inline-block; float:none; font-size:18.06px; line-height:0; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; padding:1px 0px; position:relative; white-space:nowrap; word-spacing:normal; word-wrap:normal" tabindex="0"> nên:
9x = 36 => x = 36 : 9 = 4
Vậy x = 4.
\(\dfrac{x}{4}+\dfrac{x}{5}=\dfrac{18}{10}\)
\(\dfrac{5x}{20}+\dfrac{4x}{20}=\dfrac{18}{10}\)
\(\dfrac{9x}{20}=\dfrac{18}{10}\)
\(9x=\dfrac{18\cdot20}{10}\)
\(9x=36\)
\(x=36:9\)
\(x=4\)
Vậy \(x=4\).
