题目内容
计算:(
+y)2-(
-y)2=______.
| x |
| 2 |
| x |
| 2 |
(
+y)2-(
-y)2,
=[(
+y)-(
-y)][(
+y)+(
-y)],
=[
+y-
+y)][
+y+
-y],
=2y•x,
=2xy.
| x |
| 2 |
| x |
| 2 |
=[(
| x |
| 2 |
| x |
| 2 |
| x |
| 2 |
| x |
| 2 |
=[
| x |
| 2 |
| x |
| 2 |
| x |
| 2 |
| x |
| 2 |
=2y•x,
=2xy.
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