The equation of the base of an equilateral triangle is `x+y-2=0` and the opposite vertex his coordinates (2, -1). Find the length of side of the triangle.

Explanation

To find the length of the side of the equilateral triangle given the equation of the base and the coordinates of the opposite vertex, we can follow these steps:

### Step 1: Identify the equation of the base and the coordinates of the vertex
The equation of the base of the equilateral triangle is given as:
\[ x + y - 2 = 0 \]
The coordinates of the opposite vertex are:
\[ (2, -1) \]

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