Question

Find k such that (-5,k),(2,4),(12,-1) are colinear

Answer 1

HI,

Explanation:

A=(-5,k)

B=(2,4)

C=(12,-1)

`\overrightarrow{AB}=(7,4-k)\\\overrightarrow{BC}=(10,-5)\\\\\\\overrightarrow{AB}*\alpha=\overrightarrow{BC}\\7*\alpha=10\ \Longrightarrow\ \alpha=(10)/(7) \\\\(4-k)*\alpha=-5\\\Longrightarrow\ (4-k)*(10)/(7)=-5\\\Longrightarrow\40-10*k=-35\\\\\Longrightarrow\ \boxed{k=7.5}\\`