初一数学题 在线等·高手进
来源:百度知道 编辑:UC知道 时间:2024/09/23 17:16:50
我要详细的解析与答案·在线等·高手进
若x+y+6,xy+3,求5x^2+5y^2-2xy的值
若x+y+6,xy+3,求5x^2+5y^2-2xy的值
是x+y=6,xy=3吗?
5x^2+5y^2-2xy
=5(x²+y²)-2xy
=5(x²+2xy+y²)-2xy-10xy
=5(x+y)²-12xy
代入x+y,xy的值
=5×6²-12×3
=180-36
=144
“^”是什么意思?
5x^2+5y^2-2xy
=5(x²+y²)-2xy
=5(x²+2xy+y²)-2xy-10xy
=5(x+y)²-12xy
当x+y+6,xy+3时,
原式=5×6²-12×3
=180-36
=154
原式=5x^2+5y^2+10xy-12xy
=5(x+y)^2-12xy
=5*6^2-12*3
=180-36
=144
144
5x^2+5y^2-2xy
=5(x²+y²)-2xy
=5(x²+2xy+y²)-2xy-10xy
=5(x+y)²-12xy
代入x+y,xy的值
=5×6²-12×3
=180-36
=144