(1)设m、n是一元二次方程x²+3x-7=0的两个根,则m²+4m+n=_______(2)若m、n是方程x²-3x+1=0的两根,则代数式2m²+4n²-6n+2000的值为_______;(3)已知x1、x2是方程x²+3x+1=0的两实数根,
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![(1)设m、n是一元二次方程x²+3x-7=0的两个根,则m²+4m+n=_______(2)若m、n是方程x²-3x+1=0的两根,则代数式2m²+4n²-6n+2000的值为_______;(3)已知x1、x2是方程x²+3x+1=0的两实数根,](/uploads/image/z/1123713-9-3.jpg?t=%EF%BC%881%EF%BC%89%E8%AE%BEm%E3%80%81n%E6%98%AF%E4%B8%80%E5%85%83%E4%BA%8C%E6%AC%A1%E6%96%B9%E7%A8%8Bx%26%23178%3B%2B3x-7%3D0%E7%9A%84%E4%B8%A4%E4%B8%AA%E6%A0%B9%2C%E5%88%99m%26%23178%3B%2B4m%2Bn%3D_______%EF%BC%882%EF%BC%89%E8%8B%A5m%E3%80%81n%E6%98%AF%E6%96%B9%E7%A8%8Bx%26%23178%3B-3x%2B1%3D0%E7%9A%84%E4%B8%A4%E6%A0%B9%2C%E5%88%99%E4%BB%A3%E6%95%B0%E5%BC%8F2m%26%23178%3B%2B4n%26%23178%3B-6n%2B2000%E7%9A%84%E5%80%BC%E4%B8%BA_______%EF%BC%9B%EF%BC%883%EF%BC%89%E5%B7%B2%E7%9F%A5x1%E3%80%81x2%E6%98%AF%E6%96%B9%E7%A8%8Bx%26%23178%3B%2B3x%2B1%3D0%E7%9A%84%E4%B8%A4%E5%AE%9E%E6%95%B0%E6%A0%B9%2C)
(1)设m、n是一元二次方程x²+3x-7=0的两个根,则m²+4m+n=_______(2)若m、n是方程x²-3x+1=0的两根,则代数式2m²+4n²-6n+2000的值为_______;(3)已知x1、x2是方程x²+3x+1=0的两实数根,
(1)设m、n是一元二次方程x²+3x-7=0的两个根,则m²+4m+n=_______
(2)若m、n是方程x²-3x+1=0的两根,则代数式2m²+4n²-6n+2000的值为_______;
(3)已知x1、x2是方程x²+3x+1=0的两实数根,则x1³+8x2+20=______ .
(1)设m、n是一元二次方程x²+3x-7=0的两个根,则m²+4m+n=_______(2)若m、n是方程x²-3x+1=0的两根,则代数式2m²+4n²-6n+2000的值为_______;(3)已知x1、x2是方程x²+3x+1=0的两实数根,
(1) 因为m,n为方程的两个根,有m^2-3*m-7=0
m^2+4*m+n= m^2+3*m-7 +m+7+n
=m+n+7
又因为m+n=-3
上式得-3+7=4
(2)原式等于2*m^2-6*m+2+(6*m-2)+4*n^2-12*n+4+(12*n-4)-6*n+2000
=6*m-2+6*n-4+2000
=6(m+n)+1994
=6*(-3)+1994
=1976