x2 |
25 |
y2 |
9 |
PA |
AF |
PB |
BF |
A.-
| B.-
| C.
| D.
|
PA |
AF |
PB |
BF |
x1 |
4-x1 |
x2 |
4-x2 |
x2 |
25 |
y2 |
9 |
200k2 |
9+25k2 |
400k2-225 |
9+25k2 |
x1 |
4-x1 |
x2 |
4-x2 |
4(x1+x2)-2x1x2 |
16-4(x1+x2)+x1x2 |
4•
| ||||
16-4•
|
50 |
9 |
x2 |
4 |
y2 |
2 |
A.
| B.
| C.
| D.
|
x2 |
4 |
A.r∈(0,1] | B.r∈(1,2] | C.r∈(
| D.r∈[
|
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