Distance = Square root of (y2-y1)^2 + (x2-x1)^2
Subtract the y on the left from the y on the right like this
-9 - -17 = -9 + 17 = 8
square that
8^2 = 64
Thats the (x2-x1)^2 part
Subtract the x on the left from the x on the right like this
-4 - -19 = -4 + 19 = 15
square that
15^2 = 225
That's the (y2-y1)^2 part
Using the formula distance = square root of (y2-y1)^2 + (x2-x1)^2 we now have
Distance = Sqrt(64+225)
Distance = Sqrt(289)
Distance = 17