1969 AMC 12 Question 21
AMC12 · 1969 AMC 12
If the graph of $x^2+y^2=m$ is tangent to that of $x+y=\sqrt{2m},$ then:
$m$ must equal $\dfrac12$
$m$ must equal $\dfrac1{\sqrt2}$
$m$ must equal $\sqrt2$
$m$ must equal $2$
$m$ may be any nonnegative real number