/question/562056664.html？ Fr = qlquick # answer-1411387986

Let the height on the side of AO be h.

Then s = 0.5h

When x= root number 2. S= 1/2 max？ So the answer must be a or c.

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As shown in the figure or attachment, it can be known from the topic that H has the maximum value about X, so the image opening of H is downward, so the image opening of S about X is downward, so A is correct.