Question 1115411

equation of the line is: 
{{{y=mx+b}}} where {{{m}}} is gradient and {{{b}}} is y-intercept

if given {{{m=3}}} and point ({{{-1}}},{{{3}}}), we have

{{{3=3(-1)+b}}}.... solve for {{{b}}}

{{{3=-3+b}}}

{{{3+3=b}}}

{{{b=6}}}

plug {{{m=3}}} and {{{b=6}}} in {{{y=mx+b}}}

{{{y=3x+6}}}=> your equation


check:

{{{drawing( 600, 600, -10, 10, -10, 10,
circle(-1,3,.12),locate(-1,3,p(-1,3)),
 graph( 600, 600, -10, 10, -10, 10, 3x+6)) }}}