math117: fix spam

docs/ce1/math115.md

@@ -259,3 +259,7 @@ $$
     Vectors of different dimensions cannot be compared — the missing dimensions cannot be treated as 0.
 
 The standard form of a vector is written as the difference between two points: $\vec{OA}$ where $O$ is the origin and $A$ is any point. $\vec{AB}$ is the vector as a difference between two points.
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+### Linear combination
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docs/ce1/math117.md

@@ -43,7 +43,6 @@ If a function is not invertible, restricting the domain may allow a **partial in
     By restricting the domain to $[0,\inf]$, the **multivalued inverse function** $y=\pm\sqrt{x}$ is reduced to just the partial inverse $y=\sqrt{x}$.
 
 ## Symmetry
-78u7u887878
 An **even function** satisfies the property that $f(x)=f(-x)$, indicating that it is unchanged by a reflection across the y-axis.
 
 An **odd function** satisfies the property that $-f(x)=f(-x)$, indicating that it is unchanged by a 180° rotation about the origin.