the third graph is y = - 5x + 1
The equation of a line in ' slope- intercept form ' is
y = mx + c ( m is the slope and c the y-intercept )
y = - 5x + 1 is in this form with m = - 5 and c = 1
Since the slope is negative the line will slope down from left to right.
Graphs 3/4 are the only 2 which slope down
Both graphs have a y -intercept of 1
Only graph 3 has a slope of - 5
check using the points (0 ,1 ) and ( 1, - 4 )