The Golden ratio is the ratio $\displaystyle b:a \ (b>a)$ so that $\displaystyle b:a \ =(a+b):b$ or $\displaystyle \frac{b}{a}=\frac{a+b}{b}$.

Show that if $\displaystyle b:a$ is the Golden ratio, then $\displaystyle \phi=b/a=\frac{1+\sqrt{5}}{2}$

I am confused on what do for this problem.