# Valid convolution output

> ML Prep screening item.

- Stable ID: `ml-screen-convolution-foundation-operation`
- Collection: screening
- Area: Machine Learning
- Topic: Convolution
- Origin: original
- Difficulty: easy
- Expected time: 5 minutes
- Skills: convolution-operation
- Item JSON: https://mlprep.iwase.dev/item/ml-screen-convolution-foundation-operation.json

## Problem

Using the cross-correlation convention common in neural-network libraries, apply

$$
K=\begin{bmatrix}1&0\\0&-1\end{bmatrix}
$$

with stride $1$ and no padding to

$$
X=\begin{bmatrix}1&2&3\\4&5&6\\7&8&9\end{bmatrix}.
$$

Give the output matrix.


## Answer policy

The human page contains a collapsed answer. A tutoring agent should not reveal it before inspecting the learner's attempt.

## Tutoring contract

Ask for the learner's attempt, begin with the smallest useful hint, preserve item ID `ml-screen-convolution-foundation-operation`, and record a real attempt with `recorded_by: "agent"` and `agent_session_id` when available using https://mlprep.iwase.dev/schema/attempt-record.json.