Answer:
38 cm
Explanation:
the equation for a rectangle is A = LW
84 = LW
we know that one side is 5 cm longer so
L = W + 5
substitute this into the equation
84 = LW
84 = W(W+5)
84 = W^2 + 5W
move all terms to one side
W^2 + 5W - 84 = 0
factor and find two numbers whose product is -84 and sum is 5
(W + 12)(W - 7) = 0
set both terms equal to 0
W + 12 = 0, W - 7 = 0
W = -12, 7
since width cant be negative, W = 7
L = W + 5 = 7 + 5 = 12
so W = 7 and L = 12
plug these values into perimeter = 2(W + L)
perimeter = 2(12 + 7)
= 2(19)
= 38 cm