Answer
$none$ $of$ $the$ $solutions$ $are$ $extraneous$
Work Step by Step
$Given,$ $-t=\sqrt (-6t-5)$
Checking for $t=-5$:
$L.H.S=-(-5)=5$
$R.H.S=\sqrt ((-6X-5)-5)=\sqrt (30-5)=\sqrt 25=5$
$L.H.S=R.H.S$,hence not extraneous
Checking for $t=-1$:
$L.H.S=-(-1)=1$
$R.H.S=\sqrt ((-6X-1)-5)=\sqrt (6-5)=\sqrt 1=1$
$L.H.S=R.H.S$,hence not extraneous