Question 173898
The staring point would be
{{{m = (y - y[1]) / (x - x[1])}}}
Where m = slope and ({{{x[1]}}},{{{y[1]}}}) is a 
known point on the line
Now if you multiply both sides by {{{x - x[1]}}}, you get
{{{y - y[1] = m*(x - x[1])}}}
At this point, if you're given {{{m}}} and
({{{x[1]}}},{{{y[1]}}}) you can just plug those values in
and put the equation in the form {{{y = mx + b}}}.
If nothing more is given, though, you can still put this 
in the form {{{y = mx + b}}}
{{{y - y[1] = m*(x - x[1])}}}
{{{y = m*(x - x[1]) + y[1]}}}
{{{y = mx - m*x[1] + y[1]}}} answer
The 2 terms together {{{ -m*x[1] + y[1]}}} equal {{{b}}},
the y-intercept in {{{y = mx + b}}}
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For an example, say {{{m = 2}}} and {{{x[1] = 3}}},{{{y[1] = 7}}}
{{{y = mx - m*x[1] + y[1]}}}
{{{y = 2x - 2*3 + 7}}}
{{{y = 2x - 6 + 7}}}
{{{y = 2x + 1}}}
{{{b = 1}}}
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Now just plugging in the data into {{{y = mx + b}}}, I get
{{{7 = 2*3 + b}}}
{{{b = 7 - 6}}}
{{{b = 1}}}
OK