Question 979535
Substitute.
Let {{{u=t^(1/3)}}}
Then,
{{{49u^2+28u+4=0}}}
{{{(7u+2)^2=0}}}
{{{7u+2=0}}}
{{{7u=-2}}}
{{{u=-2/7}}}
{{{t^(1/3)=-2/7}}}
{{{t=(-2/7)^3}}}
{{{t=-8/343}}}