Challenge C

Writing equations given slope and a point 

Writing Equations given Two Points 

To find a parallel or perpendicular line, first put the given equation in slope intercept form.

Parallel lines have the SAME slope, so use the slope from the given equation (after putting it in y=mx+b form) and the point given to write the equation.

Perpendicular lines have opposite inverse slopes, so, if the slope from the original equation in slope intercept form is 2, the opposite inverse slope would be -1/2.  If the original slope is -3/4, the perpendicular slope would be 4/3.  You flip the fraction and change the sign.  Then use the new slope and the point given to write the equation like we did in hint #1.