20 10 the answer to the last question of the mathematics examination questions for the senior high school entrance examination in Guang 'an.

The analytical formula is simple: y = x 2-3x-4.

Then e is the largest when it is the vertex of the parabola.

Vertex (3/2, 25/4) is found by vertex.

(3/2) Substitute into a straight line to get P(3/2, -5/2).

then

(! Let CQ be perpendicular to the y axis.

Q(0，-4)

The focus of parabola on the Y axis is exactly (0,4).

So q passes through a parabola, so we can know that q is symmetrical about the straight line PE in C, and PQ=PC.

Easy-to-get PC=3 root numbers 2/2

QC=3

In proportion, it is an isosceles right triangle right angle.

(! ! Therefore, it is easy to know that there is no other situation in the triangle with PC as the right angle.

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