Question

)The equation of the line of best fit of a scatter plot is y = −4x − 6. What is the the y-intercept?

Answer 1

Well the y-intercept is where a line crosses the y-axis 
y=-4x-6
think of it as y=mx+b
m is always going to be your slope 
b is always going to be your y-intercept
y-intercept of y=-4x-6
is -6

Answer 2

First of all, to make this problems more clearly. I will use slope-intercept form in this case which is
y=mx+b where m represent slope and b represent y-intercept
Then, we analyze the same to y=-4x-6
m=-5
y=-6 or y-intercept=-6. As a result, the y-intercept is -6. Hope it help!