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 Question from T.S., a parent: for which value of w does the rectangle below have an area of 864 square units if sides are width=w+15 and length=w-15

The area of a rectangle is the length times the width. You have a length of $w - 15$ units and a width od $w + 15$ units and hence the area is $(w - 15) \times (w + 15)$ square units. But the problem states that the area is 864 square units and thus

$(w - 15) \times (w + 15) = 864.$

Expand the left side and solve for $w.$

Penny

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