diff --git a/numpy_questions.py b/numpy_questions.py
index 07a10c1..250ccd3 100644
--- a/numpy_questions.py
+++ b/numpy_questions.py
@@ -40,7 +40,16 @@ def max_index(X):
     i = 0
     j = 0
 
-    # TODO
+    # On vérifie que l'entrée est un tableau numpy
+    if not isinstance(X, np.ndarray):
+        raise ValueError("Input array must be 2d")
+
+    # On vérifie que le tableau est en 2D
+    if X.ndim != 2:
+        raise ValueError("Input array must be 2d")
+
+    # cherche l'indice du maximum
+    i, j = np.unravel_index(np.argmax(X), X.shape)
 
     return i, j
 
@@ -62,6 +71,15 @@ def wallis_product(n_terms):
     pi : float
         The approximation of order `n_terms` of pi using the Wallis product.
     """
-    # XXX : The n_terms is an int that corresponds to the number of
-    # terms in the product. For example 10000.
-    return 0.
+    # On initialise le produit à 1
+    product = 1.0
+
+    # Formule de Wallis
+    for n in range(1, n_terms + 1):
+        term = (4 * n**2) / ((4 * n**2) - 1)
+        product *= term
+
+    # Pi est 2 fois ce produit
+    pi = 2*product
+
+    return pi