solve the equation 40a^2+4a=0
\(40a^2+4a=0\ \ \ \ |divide\ both\ sides\ by\ 4\\\\10a^2+a=0\\\\a(10a+1)=0\iff a=0\ or\ 10a+1=0\\\\a=0\ or\ 10a=-1\\\\\boxed{a=0\ or\ a=-0.1}\)