X)}^{m}}=1+mx+\
FRAC
{m(m-1)}{
2
!}{{x}^{2}}+...\] By
HYPOTHESIS
, \[\frac{m(m-1)}{2}{{x}^{2}}=-\frac{1}{8}{{x}^{2}}\] Þ \[4{{m}^{2}}-4m=-1\] Þ \[{{(2m-1)}^{2}}=0\Rightarrow m=\frac{1}{2}\].