Working of a transistor in a TTL inverter circuit
Well, you do know Q1 base collector junction is forward biassed. 

Looking at Q2 and Q3, you can put an upper limit on the collector voltage of Q1.

That allows you to determine an upper bound for Q1 base voltage.



Finally that lets you establish whether or not Q1 base-emitter is reverse biased for any value of the input (emitter) voltage.