The area of a rectangle is the product of its length and width. When that rectangle is a square, the length and width are the same. Here, they are given as "l". Then the area of the square is ...
a = l·l = l²
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The volume of a cuboid is the product of its height and the area of its base. A cube of edge length s has a square base of side length s and a height of s. Then its volume will be ...
You want to know the value of x that makes y=1000. You can plug the equation in to your calculator or desmos. Look at the table for when y=1000. X is 26.
To check, plug in 26 for x. 26^2 + 20(26) - 196 = 1000.
