Mark M. answered 01/31/21
Retired math prof. Calc 1, 2 and AP Calculus tutoring experience.
x2 + y2 = a2 is an equation of the circle with center (0,0) and radius a (Assuming that a > 0).
kx2 + ky2 = a2 can be written as x2 + y2 = (a/√k)2, which is an equation of the circle with center (0,0) and radius a/√k, if 0 < k < 1.
Since 0 < k < 1, 0 < a < a/√k. So, the given statement is FALSE. For example, if k = 1/4, then a/√k = 2a > a.