Because the straight line is to have a gradient of −3, its equation can be written as
y=−3x+m
where m is a constant. If the line is also to pass through the point xy=1−2 , the point must satisfy the equation of the line
−2=−31+m
which gives that m=1.
The answer is thus that the equation of the line is y=−3x+1.
x
y
=1−2 
1+m
