1.a+1/a=3,则a^2+1/a^2=( ).A.7 B.9 C.10 D.112.若x+y=2,x^2+y^2=15,求xy的值.3.若(x+y)^2=7,(x-y)^2=5,求xy的值.4.若M=10a^2+2b^2-7a+6,N=a^2+2b^2+5a+1,试比较M和N的大小.5.解方程:(3x+1)^2-(2x-1)^2=(x-1)(5x+2)-24.
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![1.a+1/a=3,则a^2+1/a^2=( ).A.7 B.9 C.10 D.112.若x+y=2,x^2+y^2=15,求xy的值.3.若(x+y)^2=7,(x-y)^2=5,求xy的值.4.若M=10a^2+2b^2-7a+6,N=a^2+2b^2+5a+1,试比较M和N的大小.5.解方程:(3x+1)^2-(2x-1)^2=(x-1)(5x+2)-24.](/uploads/image/z/5919433-25-3.jpg?t=1.a%2B1%2Fa%3D3%2C%E5%88%99a%5E2%2B1%2Fa%5E2%3D%28+%29.A.7+B.9+C.10+D.112.%E8%8B%A5x%2By%3D2%2Cx%5E2%2By%5E2%3D15%2C%E6%B1%82xy%E7%9A%84%E5%80%BC.3.%E8%8B%A5%28x%2By%29%5E2%3D7%2C%28x-y%29%5E2%3D5%2C%E6%B1%82xy%E7%9A%84%E5%80%BC.4.%E8%8B%A5M%3D10a%5E2%2B2b%5E2-7a%2B6%2CN%3Da%5E2%2B2b%5E2%2B5a%2B1%2C%E8%AF%95%E6%AF%94%E8%BE%83M%E5%92%8CN%E7%9A%84%E5%A4%A7%E5%B0%8F%EF%BC%8E5%EF%BC%8E%E8%A7%A3%E6%96%B9%E7%A8%8B%EF%BC%9A%283x%2B1%29%5E2-%282x-1%29%5E2%3D%28x-1%29%285x%2B2%29-24.)
1.a+1/a=3,则a^2+1/a^2=( ).A.7 B.9 C.10 D.112.若x+y=2,x^2+y^2=15,求xy的值.3.若(x+y)^2=7,(x-y)^2=5,求xy的值.4.若M=10a^2+2b^2-7a+6,N=a^2+2b^2+5a+1,试比较M和N的大小.5.解方程:(3x+1)^2-(2x-1)^2=(x-1)(5x+2)-24.
1.a+1/a=3,则a^2+1/a^2=( ).
A.7 B.9 C.10 D.11
2.若x+y=2,x^2+y^2=15,求xy的值.
3.若(x+y)^2=7,(x-y)^2=5,求xy的值.
4.若M=10a^2+2b^2-7a+6,N=a^2+2b^2+5a+1,试比较M和N的大小.
5.解方程:(3x+1)^2-(2x-1)^2=(x-1)(5x+2)-24.
1.a+1/a=3,则a^2+1/a^2=( ).A.7 B.9 C.10 D.112.若x+y=2,x^2+y^2=15,求xy的值.3.若(x+y)^2=7,(x-y)^2=5,求xy的值.4.若M=10a^2+2b^2-7a+6,N=a^2+2b^2+5a+1,试比较M和N的大小.5.解方程:(3x+1)^2-(2x-1)^2=(x-1)(5x+2)-24.
1.A
a+1/a=3,(a+1/a)^2=9即a^2+2+(1/a)^2=9
所以a^2 + 1/a^2 = 7
2.x+y=2
(x+y)^2=4
x^2+2xy+y^2=4
其中x^2+y^2=15
所以2xy=4-15=-9
xy=-4.5
3.(x+y)^2=7
x^2 + 2xy + y^2=7 (1)
(x-y)^2=9
x^2 - 2xy + y^2=9 (2)
(1)-(2)得:4xy=-2
xy=-0.5
4.M-N=9a^2+12a+5=(3a+2)^2 + 1 >0
所以M>N
5.解方程:(3x+1)^2-(2x-1)^2=(x-1)(5x+2)-24
(9x^2+6x+1)-(4x^2-4x+1)=(5x^2-3x-2)-24
9x^2+6x+1-4x^2+4x-1=5x^2-3x-26
(9x^2-4x^2-5x^2)+6x+4x+3x=-26-1
13x=-27
x=-27/13
1.A
a+1/a=3,(a+1/a)^2=9即a^2+2+(1/a)^2=9
所以a^2 + 1/a^2 = 7
2.x+y=2
(x+y)^2=4
x^2+2xy+y^2=4
其中x^2+y^2=15
所以2xy=4-15=-9
xy=-4.5
3.(x+y)^2=7
x^2 + 2xy + y^2=7 (1)
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1.A
a+1/a=3,(a+1/a)^2=9即a^2+2+(1/a)^2=9
所以a^2 + 1/a^2 = 7
2.x+y=2
(x+y)^2=4
x^2+2xy+y^2=4
其中x^2+y^2=15
所以2xy=4-15=-9
xy=-4.5
3.(x+y)^2=7
x^2 + 2xy + y^2=7 (1)
(x-y)^2=9
x^2 - 2xy + y^2=9 (2)
(1)-(2)得:4xy=-2
xy=-0.5
4.M-N=9a^2+12a+5=(3a+2)^2 + 1 >0
所以M>N
5.不会阿
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