Answer:
The answer will be D.y=-2
Step-by-step explanation:
The reflection line is the fixed line that a shape or figure is reflected across of. The problem tells you that the triangle is reflected across y=-2
If the legs are length a and b and hyptonuse is c then
a²+b²=c²
so
if the legs are 20 and 21 and the hypotnuse is x then
20²+21²=x²
400+441=x²
841=x²
29=x