If you transform x 2 + y 2 = 25 into 4x 2 + 4y 2 = 25, which option below describes the effect of this transformation on the radius?

X² + y² = 25 and 4x² + 4y² = 25

a) x² + y² =25  is a cercle which is located at (0,0) with a radius = 5

b) 4x² + 4y² = 25. We can write it 4(x²+y²) = 25 OR x²+y² = 25/4 

x²+y² = 25/4, this is a cercle which center is located at (0,0) with a radius =2.5

This transformation reduced the initial radius by half, from R = 5 to R = 2.5.