Writing equations to represent geometric problems | Grade 8 (TX TEKS) | Khan Academy

less than 1m read

·Nov 10, 2024

We're told the perimeter of the rectangle shown is 17x units. The area of the rectangle is 15x square units. Write an equation that represents the perimeter, and also write an equation that represents the area.

So pause this video and see if you can write those two equations.

All right, now let's do this together. So let's tackle this first one. Write an equation that represents the perimeter. The perimeter is going to be the length of all of the sides. So you have this side right over here which is 4x + 2, and then you're going to add this side over here, which is 2 and a half, plus this side over here which is going to be 4x + 2 again. So, plus 4x + 2, plus this side which is going to be 2 and A2 plus 2 and a half. Well, that's going to be equal to the perimeter, which they told us is 17x units. So that is going to be equal to 17x.

And we're done! That's all they wanted; they just want us to write an equation that represents the perimeter. We don't have to solve it.

So now let's do the same thing for the area. The area of a rectangle is going to be our base times our height, or our height times our base. So we could say it's 2 and A2 * (4x + 2). Then, that's going to be our area, which they say is 15x² units. So that's equal to 15x. We could have also written it the other way; we could have said that the area, which is 15x, is equal to 2 and A2, the height, times (4x + 2).

So, a lot of different ways to approach it, but in both cases, we are now done.

Yoda's Wisdom for Inner Peace (Star Wars Philosophy, Stoicism & Buddhism)

The Stock Market Crash Of 2022 | What You Must Know

View All

Bill Belichick & Ray Dalio on Having Great Relationships: Part 1

Now let’s talk about partnership. Now when you’re dealing in an organization, you have the owner, you have the players. Okay, now there’s interpersonal relations. How do you deal with those interpersonal relations? Like probably, you know the question exa…

How To Change The World? Get The Small Things Right – Dalton Caldwell and Michael Seibel

Let’s say that changing the world is like uprooting a tree, like a big old tall tree. Imagine there were two founders. One founder knew that trees have roots, and the other founder had no idea. Right? Like the trees with roots person, they have an advanta…

You’ll NEVER look at money the same way again…in under 4 minutes

Because at some point, my investment should be able to cover anything I want to buy. And that’s the point when you realize you’ve made it. What’s up, you guys? It’s Graham here. So ever since learning about compound interest and reading the book “Rich Da…

Charlie Munger's Final Advice For 2024.

I basically believe in a soldier on system. Lots of hardship will come, and you got to handle it well. I soldering through Charlie Munger, sadly passed away in November 2023, one month shy of his 100th birthday. But in a big stroke of luck for us investor…

Ross Ice Shelf Research | Continent 7: Antarctica

The Ross Ice Shelf is the largest lump of floating ice in the world. So little is known; the surface of Pluto has much better imagery than what’s beneath Raphael. It’s a lot of new stuff that we’re going to discover. No one’s ever done this before; it’s e…

Discretionary and rulemaking authority of the federal bureaucracy | Khan Academy

In many videos, we have talked about how a bill can become a law. It first gets introduced into the legislative branch, which in the United States is the U.S. Congress at the federal level. If it passes both houses of Congress, then the bill will go to th…

Writing equations to represent geometric problems | Grade 8 (TX TEKS) | Khan Academy

More Articles