Question 254831
y-intercept = -1 means when the value of x coordinate is 0 the value of y coordinate is -1

given that the line decreases by 3 when x increases by 1

so when the x coordinate is 1 the y coordinate will be -1-3 = -4

so we have two points (0,-1) and (1,-4) 

the eq is y-(-1)=[(-4+1)/(1-0)]  *(x-0)

that is y+1=-3x

that is 3x+y+1=0