Algebra-2

If the area  of a rectangle varies jointly with its length  and width , this means that when the length and width change, the area changes in proportion to the product of the length and width.

 

The statement “ varies jointly with  and ” is mathematically expressed as , where  is a constant. This is similar to direct variation, but in this case, the variable  depends on the product of two variables rather than just one.

 

For example, if we double both the length and the width of a rectangle, the area will be four times as large because .

 

Let's look at the other options:

B.

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