Question 33

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Jambmaths question: 

What is the value of r, if the distance between the point(4, 2) and (1,r) is 3 units

Jamb Maths Solution: 

$\begin{align}  & r=\sqrt{{{({{x}_{2}}-{{x}_{1}})}^{2}}+{{({{y}_{2}}-{{y}_{1}})}^{2}}} \\ & 3=\sqrt{{{(1-4)}^{2}}+{{(r-2)}^{2}}} \\ & {{3}^{2}}={{(-3)}^{2}}+{{r}^{2}}-4r+4 \\ & {{r}^{2}}-4r+4=0 \\ & {{(r-2)}^{2}}=0 \\ & r=2 \\\end{align}$

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