SOLUTION: If the area of the rectangle is 105 cm2. Its length is (4x � 5) cm and breadth is (2x � 5) cm, find the perimeter?

Question 935724: If the area of the rectangle is 105 cm2. Its length is (4x � 5) cm and breadth is (2x � 5) cm, find the perimeter?

Answer by TimothyLamb(4379) (Show Source): You can put this solution on YOUR website!
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L = 4x � 5
W = 2x � 5
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(4x � 5)(2x � 5) = 105
8xx � 20x - 10x + 25 = 105
8xx � 30x - 80 = 0
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the above quadratic equation is in standard form, with a=8, b=-30 and c=-80
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to solve the quadratic equation, by using the quadratic formula, copy and paste this:
8 -30 -80
into this solver: https://sooeet.com/math/quadratic-equation-solver.php
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the quadratic has two real roots at:
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x = 5.55136029
x = -1.80136029
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x = 13.6509717
L = 4x - 5
L = 4*13.6509717 - 5
L = 49.6038868
W = 2x - 5
W = 2*13.6509717 - 5
W = 22.3019434
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x = -1.80136029
L = 4x - 5
L = 4*-1.80136029 - 5
L = -12.20544116
W = 2x - 5
W = 2*-1.80136029 - 5
W = -8.60272058
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the negative root doesn't fit the problem statement, so use the positive root:
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answer:
p = 2L + 2W
p = 2*49.6038868 + 2*22.3019434
p = 143.8116604 cm
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