Question

What is the equation of the line that has a slope of -1 and goes through point (0, 5)?

Answer 1

y = mx + b
m = -1
y = -x + b
passes through (0,5)
put x = 0, y = 5 and solve for b

Answer 2

equation of a line is in the form y=mx+c
where m is the slope and c is the y intercept

so here slope is -1 so m=-1
so the equation becomes
y=-x+c
to find c, you substitute (0,5) in x and y
5=-1*0+c
so c=5