Answers:
Slope = 3
y intercept = -20
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The two points (0,-5) and (1,-2) are on the line y = 3x-5. You can see this through a graph, or by plugging in x = 0 to get y = -5 (do the same for x = 1 to get y = -2). The point (0,-5) is the y intercept as this is where the graph crosses the y axis.
Multiply each coordinate of those two points by the scale factor 4
(0,-5) turns into (0,-20)
(1,-2) turns into (4,-8)
Find the slope of the line through the two new points (0,-20) and (4,-8). Use the slope formula.
m = (y2-y1)/(x2-x1)
m = (-8-(-20)/(4-0)
m = (-8+20)/(4-0)
m = 12/4
m = 3
Note how the slope we just found is the same as the slope of the original line. Dilations preserve slopes, so that means the image is parallel to the preimage.
Since (0,-5) became (0,-20), this means the y intercept is now b = -20
So m = 3 and b = -20 means y = mx+b becomes y = 3x-20. Plug in x = 4 and you'll find that y = -8; proving that (4,-8) is on the line y = 3x-20.
