Question 81836
f(x)=-2x+7 
  

This is the graph of a straight line whose y intercept is 7 and whose slope is -2.  There are several ways to graph it, but it should look like this:

{{{graph(300,300,-10,10,-10,10, -2x+7 ) }}}


For your second question:
if f(x)=4x-3 find f(-1).  This means that x=-1, so substitute this for x:
f(-1) =4(-1) -3
f(-1)=-7


R^2 at SCC