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If `A` is a square matrix such that `A^2=A` , then write the value of `7A-(I+A)^3,` where `I` is the identity matrix.

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Given that,
`A`is a square matrix
`A^2=A`

`7A-(I+A)^3=7A-I^3-A^3-3A^2I-3I^2A`
`7A-(I+A)^3=7A-I-A^3-3A^2-3A`
`7A-(I+A)^3=7A-I-A^3-3A-3A`
`7A-(I+A)^3=7A-I-A^3-6A`
`7A-(I+A)^3=A-I-A^3`
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