若x+y=负1,xy=负5,求2x的平方+2y的平方的值
若x+y=负1,xy=负5,求2x的平方+2y的平方的值
还有一道题:已知x的平方-4y的平方=6,x+2y=3,求x,y的值.
还有一道题:已知x的平方-4y的平方=6,x+2y=3,求x,y的值.
数学人气:692 ℃时间:2019-10-31 04:12:29
优质解答
x+y=-1 两边同时平方得 x²+2xy+y²=(-1)² (x²+y²)+2xy=1 代入xy=-5得 (x²+y²)+2×(-5)=1 x²+y²=112x²+2y²=22x²-4y²=6 用平方差公式分解得 (x+2y)(...
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