## Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

The statement $2+4+6++2n=n^2+n+2$ is not true by the Principal of Mathematical Induction.
The principle of mathematical induction states: a) The statement must hold for the first natural number, known as the base case. b) Assume that the statement is true for some arbitrary natural number $n$ larger than the first natural number. Then we will prove that the statement also holds for $n + 1$. This is known as the inductive step. We need to prove that $2+4+6++2n=n^2+n+2$ is true for all natural numbers. Let us check for $n=k$ So, we have: $2+4+6++2k=k^2+k+2$ Let us check for $n=k+1$. So, we have: $2+4+6++2k+2(k+1)=k^2+k+2+2(k+1)\\=k^2+3k+4\\=k^2+2k+1+(k+1)+2\\=(k+1)^2+(k+1)+2$ Let us check for $n=1$. We have: $2 \ne (1)^2+1+2\implies 2\ne 4$ So, $p(1)$ is not true. Thus, the statement $2+4+6++2n=n^2+n+2$ is not true by the Principal of Mathematical Induction.