giải hpt x+y =800 23/20 x – 6/5 y =255 cần gấp ạ

2 bình luận về “giải hpt x+y =800 23/20 x – 6/5 y =255 cần gấp ạ”

1. $\begin{cases} x+y=800\\\dfrac{23}{20}x – \dfrac{6}{5}y = 255 \end{cases}$

   <=> $\begin{cases} x=800-y\\\dfrac{23}{20}x – \dfrac{6}{5}y = 255 \end{cases}$

   <=> $\begin{cases} x=800-y\\\dfrac{23}{20}.(800-y) – \dfrac{6}{5}y = 255 \end{cases}$

   <=> $\begin{cases} x=800-y\\920-\dfrac{23y}{20} – \dfrac{6y}{5} = 255 \end{cases}$

   <=> $\begin{cases} x=800-y\\920-(\dfrac{23y}{20} + \dfrac{6y}{5}) = 255 \end{cases}$

   <=> $\begin{cases} x=800-y\\920-\dfrac{47y}{20} = 255 \end{cases}$

   <=> $\begin{cases} x=800-y\\920-255 = \dfrac{47y}{20} \end{cases}$

   <=> $\begin{cases} x=800-y\\665 = \dfrac{47y}{20} \end{cases}$

   <=> $\begin{cases} x=800-y\\\dfrac{47y}{20} = 665\end{cases}$

   <=> $\begin{cases} x=800-y\\47y.1 = 665.20\end{cases}$

   <=> $\begin{cases} x=800-y\\47y = 13300\end{cases}$

   <=> $\begin{cases} x=800-y\\y = \dfrac{13300}{47}\end{cases}$

   <=> $\begin{cases} x=800-\dfrac{13300}{47}\\y = \dfrac{13300}{47}\end{cases}$

   <=> $\begin{cases} x=\dfrac{24300}{47}\\y = \dfrac{13300}{47}\end{cases}$

    Vậy: (x;y) = (\frac{24300}{47};\frac{13300}{47})

   Trả lời
2. $\left \{ {{x + y = 800} \atop {$\frac{23}{20}x$ – $\frac{6}{5}y$ = 255 }} \right.$

   ⇔ $\left \{ {{x = 800 – y} \atop {$\frac{23}{20}(800 – y)$ – $\frac{6}{5}y$ = 255 }} \right.$

   ⇔ $\left \{ {{x = 800 – y} \atop {920 – $\frac{1}{20}y$ = 255 }} \right.$

   ⇔ $\left \{ {{x = 800 – 13 300} \atop {y = 13 300}} \right.$

   ⇔ $\left \{ {{x = – 12 500} \atop {y = 13 900}} \right.$

   Trả lời