These adjectives are synonyms to ’tud, -hat, -het’. There are two ways to use them:

képes/képtelen +
lenni conjugated +
noun with suffix -ra, -re

OR

képes/képtelen +
lenni conjugated +
verb in infinitive form

Remember the predicative adjectives! It is about the same thing now. You don’t use ’lenni’ in 3rd PS and 3rd PP in present tense! The plural for these adjectives is:

képesek, képtelenek

As for these adjectives, definite and indefinite conjugation is an irrelevant issue because they require the infinitive of the verb, which refers to both definite and indefinite.

PRESENT
Képes megtenni. – He’s able to do it.
Képtelen megtenni. – He’s unable to do it.

PAST
Képes volt megtenni. – He was able to do it.
Képtelen volt megtenni.- He was unable to do it.

FUTURE
Képes lesz megtenni. – He’ll be able to do it.
Képtelen lesz megtenni. – He’ll be unable to do it.

PRESENT CONDITIONAL
Képes volna megtenni. – He would be able to do it.
Képtelen volna megtenni. – He would be unable to do it.

PAST CONDITIONAL
Képes lett volna megtenni. – He would have been able to do it.
Képtelen lett volna megtenni. – He would have been unable to do it.

Examples:

Képes vagyok rá. – I can do that.
Képtelen vagyok rá. – I can’t do that.
Képesek voltak hazudni! – They lied right to our faces!
Képtelenek voltunk megtenni. – We were incapable of that.
Képes volnál itt hagyni? – You would just leave me here?

So you can use a noun or an infinitive like in English:

-Képes vagy a feladat megoldására? -Képes vagyok rá.
-Are you capable of solving the task? -I am capable of that.

-Képes vagy megoldani a feladatot? -Képes vagyok megoldani.
-Are you able to solve the task? -I am able to solve it.

More next time.