Answer:
Answer is given below with explanations.
Step-by-step explanation:
[tex]given \: \: l = 5x - y \: and \: \: b = x + 4y \\ area \: of \: rectangle \:= l \times b \: sq.units \\ = (5x - y)(x + 4y) \\ = 5 {x}^{2} + 20xy - xy - 4 {y}^{2} \\ = 5 {x}^{2} + 19xy - 4 {y}^{2} \\ perimeter \: of \: rectangle \\ = 2(l + b) \\ = 2(5x - y + x + 4y) \\ = 2(6x + 3y) \\ = 12x + 6y[/tex]
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