what is the equation of a line with a slope 2 and passes through (0,-4)?

Answer 1

you're given both the value of the slope and y-intercept directly here! so you can just plug those into the slope-intercept form and evaluate!

y = mx + b

y = 2x - 4

Answer 2

y=ax+b

a= 2 given

substitute (0,-4)in, we get b=-4

and therefore

y=2x-4