If $\;f(x) = (\large\frac{3}{5})^{x}+ (\large\frac{4}{5})^{x}-1\;,x \in R \;$, then the equation $\;f(x) =0\;$ has :

Question

$(a)\;no\;solution\qquad(b)\;one\;solution\qquad(c)\;two\;solutions\qquad(d)\;more \;than\;two\;solutions$