[問題]GWD 3-31

[hoojjj]

Q31:
A small, rectangular park has a perimeter of 560 feet and a diagonal measurement of 200 feet. What is its area, in square feet?

A. 19,200
B. 19,600
C. 20,000
D. 20,400
E. 20,800

x+y=280
x^2+y^2=200^2
是用這兩個方程式解嗎
數據好大....解不出
謝謝解惑

[liwuu]

x+y=280
x^2+y^2=200^2

題目問面積,即求xy即可
所以不用直接解出x與y的值,用以下式子
(x+y)^2=x^2+2xy+y^2
(280)^2=(200)^2+2xy
xy=19200