Question 804761
The equation we are looking for is perpendicular to {{{y=2x+3}}}.
look at the slope 2.  to make it perpendicular you must flip it and take its opposite.
2 can be written as {{{2/1}}}.
flip it {{{1/2}}}.
take its opposite {{{-1/2}}}.
the new equation is 
{{{y=(-1/2)x+b}}}
Now you need to find be so plug the point (4,-7) into the above equation.
{{{-7=(-1/2)4+b}}}
{{{-7=-2+b}}}
{{{b=-5}}}
now plug it into the equation.
{{{y=(-1/2)x-5}}} is the new equation.