we have
m=-2
point (1,2)
step 1
find the equation of the line in point slope form
y-3=-2(x-1)
convert to slope intercept form
y-3=-2x+2
y=-2x+2+3
y=-2x+5
To graph the line we need two points
Find the y-intercept (value of y when the value of x is equal to zero)
For x=0
y=5
so
the y-intercept is (0,5)
Find the x-intercept
Value of x when the value of y is equal to zero
For y=0
0=-2x+5
2x=5
x=2.5
the xintercept is (2.5,0)
Plot the points (0,5) and (2.5,0), join them and graph the line
using a graphing tool
see the attached figure
please wait a minute