Prove by induction that `4+8+12++4n=2n(n+1)` for all `n Ndot`

Explanation

Let P(n) denote the statement
`4 + 8 + … + 4n = 2n(n + 1) `


i.e., `P(n) : 4 + 8 + 12 + … + 4n = 2n(n + 1) `

Put `n = 1, P(1)`


`LHS = 4 `

`RHS = 2 (1)(1 + 1) = 4 `

`P(1)` is true.
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