Answer: tu as cherché
Explanation:
To find a verb in the past tense in avoir, you take the present form of the verb in nous (so for chercher it would be cherchons) and then take off the “ons” at the end (to get cherch). then, you find the appropriate ending, which is é for verbs ending in “er”, and add it to the end to make it “cherché”
Next, in order to find the helping verb, these are the passe compose helping verbs in avoir:
j’ai
tu as
il/elle/on a
nous avons
vous avez
ils/elles ont
Since we are using “tu”, we would use “tu as”
So the final answer is:
Tu as cherché