> 数学 >
已知x+y=5,xy=-6,求3x^2+3y^2
人气:408 ℃ 时间:2020-01-28 21:00:14
解答
解3x^2+3y^2
=3(x^2+y^2)
=3(x^2+y^2+2xy-2xy)
=3[(x+y)^2-2xy]
=3[(5)^2-2×(-6)]
=3×(25+12)
=3×37
=111.
推荐
猜你喜欢
© 2024 79432.Com All Rights Reserved.
电脑版|手机版