Vgln. eerste graad (reeks 4)

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\(\frac{x}{6}+\frac{2}{9}=\frac{7}{5}x-5\)

\(\text{90 is het kleinste gemene veelvoud van 6, 9 en 5} \\ \begin{align} & \frac{x}{6}+\frac{2}{9}& = & \frac{7}{5}x-5 \\\Leftrightarrow & \color{blue}{90.} (\frac{15x}{ \color{blue}{90} }+ \frac{ 20 }{ \color{blue}{90} })& = & (\frac{126}{ \color{blue}{90} }x-\frac{450}{ \color{blue}{90} }) \color{blue}{.90} \\\Leftrightarrow & 15x+20& = & 126x-450 \\\Leftrightarrow & 15x \color{red}{+20} \color{blue}{-20} \color{blue}{-126x} & = & \color{red}{126x} -450 \color{blue}{-126x} \color{blue}{-20} \\\Leftrightarrow & -111x& = & -470 \\\Leftrightarrow & \frac{-111x}{ \color{red}{-111} }& = & \frac{-470}{-111} \\\Leftrightarrow & x = \frac{470}{111} & & \\ & V = \left\{ \frac{470}{111} \right\} & \\\end{align}\)