hello just started school 2 days ago. and we were told to copy down some examples and there was one were i think there is a mistake but not sure.

Use mathematical induction to prove

$\displaystyle 3^n >= 2n + 5$ for all integers

i understand all the steps untill it does this.

$\displaystyle 3^(k+1) >= 2(2k+5)$

$\displaystyle 3^(k+1) >= 6+15$

$\displaystyle 3^(k+1) >= 2k+7 $ <This line i do not understand.

Therefore

$\displaystyle 3^(k+1) >= 2(k+1) + 5$ <This line i do not understand.

could some one prove this is true or false..

Thanks in advance.