[tex]\bf ~~~~~~~~~~~~\textit{internal division of a line segment}
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J(-2,1)\qquad K(4,5)\qquad
\qquad \stackrel{\textit{ratio from J to K}}{3:7}
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\cfrac{J\underline{P}}{\underline{P} K} = \cfrac{3}{7}\implies \cfrac{J}{K} = \cfrac{3}{7}\implies 7J=3K\implies 7(-2,1)=3(4,5)\\\\
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[tex]\bf P=\left(\cfrac{\textit{sum of "x" values}}{\textit{sum of ratios}}\quad ,\quad \cfrac{\textit{sum of "y" values}}{\textit{sum of ratios}}\right)\\\\
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P=\left(\cfrac{(7\cdot -2)+(3\cdot 4)}{3+7}\quad ,\quad \cfrac{(7\cdot 1)+(3\cdot 5)}{3+7}\right)
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P=\left( \cfrac{-14+12}{7}~~,~~\cfrac{7+15}{7} \right)\implies P=\left(-\frac{2}{7}~~,~~\frac{22}{7} \right)\\
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P=\left(-\frac{2}{7}~~,~~3\frac{1}{7} \right)[/tex]