(1)若x²+y²=3,x-y=2,求xy的值.(2)已知a+b=5,ab=3,求a²+b²的值.请把解题过程写清楚.
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(1)若x²+y²=3,x-y=2,求xy的值.(2)已知a+b=5,ab=3,求a²+b²的值.请把解题过程写清楚.
(1)若x²+y²=3,x-y=2,求xy的值.
(2)已知a+b=5,ab=3,求a²+b²的值.
请把解题过程写清楚.
(1)若x²+y²=3,x-y=2,求xy的值.(2)已知a+b=5,ab=3,求a²+b²的值.请把解题过程写清楚.
(1)
x-y = 2,因此(x-y)² = 4 = x²-2xy+y² = 3-2xy
因此xy = (3-4)/2 = -1/2
(2)
a²+b² = (a+b)² - 2ab = 5² - 2×3 = 25 - 6 = 19