It's no problem! We all go through problems which just are too much info at first sight (which I can see how this would be one).

We can't. That's exactly what I am saying. Recall that if

is bounded from below then

if and only if

is a lower bound for

.

So, to show that

it suffices to show that

is a lower bound for

and similarly to show that

it suffices to show that

is a lower bound for

.

But, to make things easier (we're back to the general case now) recall that to show that

is a lower bound of

it suffices to show that

for all

.

Can you apply this?