Answer:
Width: 7
Length: 14
Step-by-step explanation:
The area of a rectangle can be found my multiplying the length by the width. We do not know neither the length nor the width. However, we do know that the length is 7 feet longer than the width. Because we do not know the value of either side, let's let
represent the width.
Since the length is 7 feet longer, we can represent the length by
.
Now that we have our values for the length and the width we can multiply them together to find our area.
![(x)(x+7)=x^{2} +7x](https://tex.z-dn.net/?f=%28x%29%28x%2B7%29%3Dx%5E%7B2%7D%20%2B7x)
Now we have our equation, so we can address the changes made by the original question. The original question states that when 7 is added to both the length and width the area becomes 3 times larger. To do so simply increase each side by 7 by adding 7 to the original values.
![(x+7)(x+14)](https://tex.z-dn.net/?f=%28x%2B7%29%28x%2B14%29)
And multiply our area by 3.
![3(x^{2} +7x)](https://tex.z-dn.net/?f=3%28x%5E%7B2%7D%20%2B7x%29)
set these equal to each other to find your new equation.
![(x+7)(x+14)=3(x^{2} +7x)](https://tex.z-dn.net/?f=%28x%2B7%29%28x%2B14%29%3D3%28x%5E%7B2%7D%20%2B7x%29)
Now you need to solve for
. To do this first muliply
and
.
![(x+7)(x+14)=\\x^{2} +14x+7x+98=\\x^{2} +21x+98](https://tex.z-dn.net/?f=%28x%2B7%29%28x%2B14%29%3D%5C%5Cx%5E%7B2%7D%20%2B14x%2B7x%2B98%3D%5C%5Cx%5E%7B2%7D%20%2B21x%2B98)
Then multiply ![3(x^{2} +7x)](https://tex.z-dn.net/?f=3%28x%5E%7B2%7D%20%2B7x%29)
![3(x^{2} +7x)=\\3x^{2} +21x](https://tex.z-dn.net/?f=3%28x%5E%7B2%7D%20%2B7x%29%3D%5C%5C3x%5E%7B2%7D%20%2B21x)
Now you can begin solving for
.
![x^{2} +21x+98=3x^{2} +21x](https://tex.z-dn.net/?f=x%5E%7B2%7D%20%2B21x%2B98%3D3x%5E%7B2%7D%20%2B21x)
Subtract
from both sides.
![21x+98=2x^{2} +21x](https://tex.z-dn.net/?f=21x%2B98%3D2x%5E%7B2%7D%20%2B21x)
Subtract
from both sides.
![98=2x^{2}](https://tex.z-dn.net/?f=98%3D2x%5E%7B2%7D)
Divide by 2.
![49=x^{2}](https://tex.z-dn.net/?f=49%3Dx%5E%7B2%7D)
And finally take the sqaure root of both sides.
![\sqrt{x^{2} }=\sqrt{49}\\x=7](https://tex.z-dn.net/?f=%5Csqrt%7Bx%5E%7B2%7D%20%7D%3D%5Csqrt%7B49%7D%5C%5Cx%3D7)
Remember, because we are dealing with length, there cannot be negative. So while normally we would get both +7 <em>and</em> -7, in this case we <em>only </em>get +7.
Now that we have the value of
, we can plug it into our original values.
For width we simply get 7.
For length we get 7+7=14
To check our answer we cna multiply 7 by 14 to get 98. Then we can add 7 to our length and width to get 14 and 21. Multiply these together and we get 294. 294 divided by 3 is 98, proving our answer correct.