已知(a+b)²=11,(a-b)²=5求a²+b²及ab的值.
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已知(a+b)²=11,(a-b)²=5求a²+b²及ab的值.
已知(a+b)²=11,(a-b)²=5求a²+b²及ab的值.
已知(a+b)²=11,(a-b)²=5求a²+b²及ab的值.
(a+b)²=a²+2ab+b²=11
(a-b)²=a²-2ab+b²=5
两式相加,得:
2(a²+b²)=16,则:a²+b²=8
两式相减,得:
4ab=6,则ab=3/2
a²+b²=8 ab=3/2