2x^2 - π(x/2)^2 = 180
8x^2 - πx^2 = 720
x^2(8 - π) = 720
x^2 = 720 / (8 - π)
x = ±√ [720 / (8 - π)]
进一步化简,分母有理化,得
x = ±12√ [5(8 - π)] / (8 - π)