mathematical induction problem
i cannot figure out how to know that [k-1]^2 has to be ''picked-out''
i have no idea how to do this type of question also.
sorry for my bad hand-writing
You do understand that you're working towards the final line being > (k + 1)^2? So the k^2 gets replaced with (k - 1)^2 + 2k -1 because (k - 1)^2 is bigger than 2 for k > 4 and so you can write the second last line, which will give you the final line ......
It's a trick that once seen you memorise and then learn to generalise - as in the second problem, where you need to work towards the final line being > (k + 1)^3.