Question 664406
Given 
a = 780 {{{cm^2}}}, which is (l)(w)
l = w+4
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Plug and Play!
(w+4)(w) = 780
Distribute the w
{{{w^2}}} + 4w = 780
create the quadratic
{{{w^2}}} + 4w - 780 = 0
(w-  )(w+ ) mixed sign due to the + 4 and - 780
Find multiple of 780 that subtracts to 4:  30,26
(w-26)(w+30)
w-26=0, so w=26
w+30=0, so w=-30
Width cannot be negative, so the width is 26 cm
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l = 26 + 4 = 30 cm is the length
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Check
a = 26(30) = 780
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