Question 947392
{{{f(x)=mx+b}}}
{{{m=(y[2]-y[1])/(x[2]-x[1])=(15-3)/(9-6)=12/3=4}}}
{{{f(x)=4x+b}}}
{{{f(6)=4(6)+b=3}}}
{{{24+b=3}}}
{{{b=-21}}}
So,
{{{highlight(f(x)=4x-21)}}}