###Where can I find this?
You’ll find everything you need for this lesson in [Lesson 2](/math/4th-grade-illustrative-mathematics/xa755074f458c4b7e:factors-and-multiples/xa755074f458c4b7e:factor-pairs/v/creating-rectangles-with-a-given-area-1-math-3rd-grade-khan-academy), where we cover this and more all in one place. This way, you can learn about it all at once, without any extra steps.