diff --git a/DIRECTORY.md b/DIRECTORY.md
index 00f4bb4ef2b2..dfecc9cfe584 100644
--- a/DIRECTORY.md
+++ b/DIRECTORY.md
@@ -443,6 +443,7 @@
   * [Present Value](financial/present_value.py)
   * [Price Plus Tax](financial/price_plus_tax.py)
   * [Simple Moving Average](financial/simple_moving_average.py)
+  * [Straight Line Depreciation](financial/straight_line_depreciation.py)
   * [Time And Half Pay](financial/time_and_half_pay.py)
 
 ## Fractals
diff --git a/maths/radix2_fft.py b/maths/radix2_fft.py
index ccd5cdcc0160..fc71f98ec0be 100644
--- a/maths/radix2_fft.py
+++ b/maths/radix2_fft.py
@@ -159,13 +159,13 @@ def __multiply(self):
     # Overwrite __str__ for print(); Shows A, B and A*B
     def __str__(self):
         a = "A = " + " + ".join(
-            f"{coef}*x^{i}" for coef, i in enumerate(self.polyA[: self.len_A])
+            f"{coef}*x^{i}" for i, coef in enumerate(self.polyA[: self.len_A])
         )
         b = "B = " + " + ".join(
-            f"{coef}*x^{i}" for coef, i in enumerate(self.polyB[: self.len_B])
+            f"{coef}*x^{i}" for i, coef in enumerate(self.polyB[: self.len_B])
         )
         c = "A*B = " + " + ".join(
-            f"{coef}*x^{i}" for coef, i in enumerate(self.product)
+            f"{coef}*x^{i}" for i, coef in enumerate(self.product)
         )
 
         return f"{a}\n{b}\n{c}"