Mathematics

Problem

The function

m(x)=x^{5/2}-2x^{3/2}

is defined for

x\ge 0

. For which value(s) of

x

does the graph of

m

have a horizontal tangent line? a)

\{6/5\}

\{0,\;6/5\}

\{0,\;3/5\}

\{0,\;2\}