If the points (3,7), (1,k) and (-1,1) are collinear, what is the value of k?
1 Answer
Mar 17, 2018
Explanation:
the points are collinear thus lie in a line
since they are in a line then the slope between points
will be equal
calculate slope between (3,7) and (−1,1)
∙xm=y2−y1x2−x1←gradient formula
let (x1,y1)=(3,7) and (x2,y2)=(−1,1)
⇒m=1−7−1−3=−6−4=32
slope between (3,7) and (1,k)=32
⇒m=k−71−3=k−7−2
equating and solving for k
⇒k−7−2=32
⇒2(k−7)=−6
⇒2k−14=−6
⇒2k=8⇒k=4
