已知4x²y-3y²=7,3x²y+4y²=19,求11x²y-2y²的值

已知4x²y-3y²=7,3x²y+4y²=19,求11x²y-2y²的值
已知4x²y-3y²=7,3x²y+4y²=19,求11x²y-2y²的值

已知4x²y-3y²=7,3x²y+4y²=19,求11x²y-2y²的值
4x²y-3y²=7.(1)
3x²y+4y²=19.(2)
(1)*2+(2):
11x^2y-2y^2=14+19=33

由4x²y-3y²=7，得8x²y-6y²=14
8x²y-6y²=14与3x²y+4y²=19相加得11x²y-2y²=33