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# ExtElement + ExtElement -- addition of Ext-algebra elements

- Operator: +
- Usage:
    `u=x + y`
- Inputs:
  - x, an instance of the type ExtElement, $x$ is of type $E$, where $E$ is of type ExtAlgebra
  - y, an instance of the type ExtElement, y is of type E
- Outputs:
  - u, an instance of the type ExtElement, $u$ is of type $E$, the sum of $x$ and $y$

## Description

The symbol + is used as infix notation for the Ext-algebra addition. The elements $x$ and $y$ must have the same weight and sign.

    i1 : L = lieAlgebra{a,b,c}/{a b,b c}

    o1 = L

    o1 : LieAlgebra

    i2 : E = extAlgebra(3,L)

    o2 = E

    o2 : ExtAlgebra

    i3 : basis(2,E)

    o3 = {ext_3, ext_4}

    o3 : List

    i4 : ext_4+2 ext_3

    o4 = 2ext_3 + ext_4

    o4 : E

## See also

- ExtAlgebra -- the class of all Ext-algebras

## Ways to use this method:

- ExtElement + ExtElement -- addition of Ext-algebra elements

The source of this document is in /build/macaulay2-88fgJW/macaulay2-1.25.11+ds/M2/Macaulay2/packages/GradedLieAlgebras/doc.m2:2208:0.