What is the equation of the line that passes through point (3,-7) and has a slope -1

Answer 1

One other way...

y = mx + b

-7 = -1(3) + b

-7 = - 3 + b

b = -4

y = -x - 4

Answer 2

Use the point-slope equation for a line of slope m = –1 passing through point (x_0, y₀) = (3, –7) is

(y – y₀) = m(x – x₀)

which can be rewritten as

y = m(x – x₀) + y₀ = mx + (y₀ – mx₀)

which gives you the line in slope intercept form (y = mx +b) where b = (y₀ – mx₀)

just plug in m = –1, x₀ = 3, and y₀ = – 7 and you have the equation for your line.