Question 136162
Lines are parallel if and only if their slopes are equal.


{{{y=x}}} is in slope-intercept form {{{y=mx+b}}} with {{{m=1}}} and {{{b=0}}}, so the slope of your given line is 1.


Now you have a given point, (2, 4), and a slope, 1.


Use the point-slope form of a line to derive the desired equation:


{{{y-y[1]=m(x-x[1])}}} where m is the slope, {{{x[1]}}} and {{{y[1]}}} are the coordinates of the given point.


Once you have substituted the given values, use standard algebraic methods to put the result into standard form, which is {{{ax+by=c}}}