Determine all points on the straight line which joins $(4, 11)$ to $(16, 1)$ and whose coordinates are positive integers.
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firemonkey17
08.06.2017 05:15
We find that the slope of the line is $-\frac{3}{5}$. Finding the equation of the line by plugging in points yields $3x+5y=43$. Observation tells us that $y$ is an integer when $3x+12$ is a multiple of $5$, or when $x+4$ is a multiple of $5$. These occur every $5$ units apart, so the values are $-4,1,6,11,16$. We can plug in to find the $y$ values. Thus all the points are $(-4,11),(1,8),(6,5),(11,2),(16,-1)$.
PokeMathist
08.06.2017 08:17
Instead of posting 3 questions in different topics, put them all together.
MathArt4
09.06.2017 01:20
PokeMathist wrote: Instead of posting 3 questions in different topics, put them all together. I was making a contest collection, so I couldn't do that.