已知x1 x2是方程x²+3x+1=0的两根,则(x1)²-3(x2)²+20=_________
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![已知x1 x2是方程x²+3x+1=0的两根,则(x1)²-3(x2)²+20=_________](/uploads/image/z/10109215-55-5.jpg?t=%E5%B7%B2%E7%9F%A5x1+x2%E6%98%AF%E6%96%B9%E7%A8%8Bx%26%23178%3B%2B3x%2B1%3D0%E7%9A%84%E4%B8%A4%E6%A0%B9%2C%E5%88%99%28x1%29%26%23178%3B-3%28x2%29%26%23178%3B%2B20%3D_________)
已知x1 x2是方程x²+3x+1=0的两根,则(x1)²-3(x2)²+20=_________
已知x1 x2是方程x²+3x+1=0的两根,则(x1)²-3(x2)²+20=_________
已知x1 x2是方程x²+3x+1=0的两根,则(x1)²-3(x2)²+20=_________
已知x1 x2是方程x²+3x+1=0的两根:
X1=(√5 - 3)/2,
X2=(-√5-3)/2
则:(X1)^2=(7-3√5)/2
(X2)^2=(7+3√5)/2
(X1)²-3(X2)²+20
=3.5-1.5√5-3(3.5+1.5√5)+20
=13-6√5