The area of a square garden is A square feet and the perimeter is P feet. If A = 2P + 9, what is the perimeter of the garden, in feet?
28
36
40
56
64
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硬是没看出来 脑壳又被鬼打墙....
trapezoid 梯形
isosceles trapezoid 等腰梯形
bisector 角平分线
顺便记一下吧...
P = 4a
A = a^2
Sub in equation A=2P+9
a^2 = 8a +9
a^2-8a +9 = 0
a = 9 or -1
So P = 4*9 = 36.