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Is it possible to design a rectangular park of perimeter 80 m and area 400 m2?
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Let the length and breadth of the park be l and b.
Perimeter = 2 (l + b) = 80
l + b = 40 Or, b = 40 – l
Area = l × b = l (40 − l)
= 40l − l2= 400 Given
l2 − 40l + 400 = 0
Comparing this equation with al2 + bl + c = 0, we obtain
a = 1, b = −40, c = 400
Discriminant = b2 − 4ac = (− 40)2 −4 (1) (400) = 1600 − 1600 = 0
As b2 − 4ac = 0,
Therefore, this equation has equal real roots.
And hence, this situation is possible.
Root of this equation,
Therefore, length of park, l = 20 m
And breadth of park, b = 40 − l = 40 − 20 = 20 m
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