Saturday, December 1, 2018

algebra precalculus - Why does $k^2+4k+4$ become $(k+2)^2$?



I'm studying maths after a lot of years without having a look at it.




Currently I'm doing proof by induction, I have a doubt when doing an exercise.



If you have a look at this video at minute 5:15 , $[k^2+4k+4]$ becomes $(k+2)^2$ and I don't understand why.



Is there any rule or theorem that explains this?


Answer



depending on the area of rectangle



enter image description here




$$k^2+2k+2k+4=(k+2)(k+2)$$
$$(k^2+4k+4)=(k+2)^2$$


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