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.

Working at Big Tech Companies Can Be a Trap - Michael Seibel

Avoid these 3 Mistakes if you want to grow FAST on YouTube

View All

'Zombie' Parasite Cordyceps Fungus Takes Over Insects Through Mind Control | National Geographic

Fungi and slime molds race to decompose dead matter on the forest floor. Many spread by releasing spores up to thirty thousand a second. (scary music) If just one of these spores lands in the right place, and takes root, it can colonize a whole new area.…

Turning Roadkill Into Art | National Geographic

I think what I’m aiming for is this notion of, I guess, seduction and revulsion. Something that’s really beautiful, really lush, rubbing up against something that’s also perhaps repulsive. I’m an artist and roadkill resurrector. The first body of work th…

Marvels of an Arctic Winter | America's National Parks

As the months of winter pass, only the heartiest of creatures will be able to survive out in the open, seemingly resigned to their fate. But under the tundra, some creatures are pulling off a small biological miracle. The hibernating ground squirrel’s bod…

Derivatives of tan(x) and cot(x) | Derivative rules | AP Calculus AB | Khan Academy

We already know the derivatives of sine and cosine. We know that the derivative with respect to x of sine of x is equal to cosine of x. We know that the derivative with respect to x of cosine of x is equal to negative sine of x. So, what we want to do in…

Two Routes to the Americas | The Great Human Race

After being trapped on the Bering Land Bridge for several thousand years, our ancestors headed south in search of warmer climates and better food sources. Once people made it across the land bridge, it was like the floodgates opened up. Kent and I are spl…

My top three favourite quotes.

If you’re the smartest person in the room, you’re in the wrong room. Here’s the top three quotes that I just love to say. First one is: when you actually think that you’ve exhausted every single possibility trying to solve a problem, just remember this—…

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

More Articles