Jason builds doghouses for a pet store. Each doghouse is a wooden structure with a rectangular base that has an area of 21 square feet and a length that is 4 feet more than its width. If x represents the width of the doghouse, write an equation in the given form that can be used to determine the possible dimensions of the base of the doghouse.
ax^2+bx=c

x(x+4) = 21, or x²+4x-21 = 0

Explination: The area of a rectangle is given by multiplying the length and width of the rectangle.  We know that the length is 4 more than the width; if x represents the width, this means that the length is x+4.

The area would then be x(x+4).  We know that the area equals 21; this gives us the equation

x(x+4) = 21

Using the distributive property, we have

x(x)+x(4) = 21

x²+4x = 21

To write in standard form, subtract 21 from each side:

x²+4x-21 = 21-21

x²+4x-21 = 0

20

step-by-step explanation:

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