Question 497669
x1 + x2 / 2 = midpoint
5 + x2 / 2 = 3
5 + 1 / 2 = 3
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y1 + y2/2 = midpoint.
-11 + y2 = 5
-11 + 21 /2  = 5
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The second point is (1, 21)
Cleomenius.