You can divide other shapes into triangles. Then you use what you know about the similar or congruent angles/sides (depending on your question) to determine congruency/similarity between other shapes.
Answer:
The third one down
Step-by-step explanation:
Let x ft be the length of the base square and y ft be the height of the box.
The volume of the box is

Since the box has a volume of 15 cubic feet, then

You need to construct two squares from the metal that cost $3 per square foot.
The area of each square is
and the total cost for these two squares is 
The area of each side face is
Then the total cost for sides is 
Let S(x) be the function that represents total cost of the box, then

Find the derivative:

When
then ![12x-\dfrac{600}{x^2}=0,\\ \\12x^3=600,\\ \\x^3=50,\\ \\x=\sqrt[3]{50}\ ft.](https://tex.z-dn.net/?f=12x-%5Cdfrac%7B600%7D%7Bx%5E2%7D%3D0%2C%5C%5C%20%5C%5C12x%5E3%3D600%2C%5C%5C%20%5C%5Cx%5E3%3D50%2C%5C%5C%20%5C%5Cx%3D%5Csqrt%5B3%5D%7B50%7D%5C%20ft.)
The dimensions of the box are:
length and width - ![\sqrt[3]{50}\ ft](https://tex.z-dn.net/?f=%5Csqrt%5B3%5D%7B50%7D%5C%20ft)
height - ![\dfrac{15}{\sqrt[3]{2500}}\ ft.](https://tex.z-dn.net/?f=%5Cdfrac%7B15%7D%7B%5Csqrt%5B3%5D%7B2500%7D%7D%5C%20ft.)
Answer:
5x + 13
Step-by-step explanation:
x times 5 is 5x.
13 more than 5x is 5x + 13, or 13 + 5x. (Same thing.)