关于x的方程x²-3x+1=0的两个实数根为x1，x2， 求x2²+3x1-5=
\u2235x1\uff0cx2\u5206\u522b\u662f\u65b9\u7a0bx²\uff0b3x\uff0b1\uff1d0\u7684\u4e24\u4e2a\u5b9e\u6570\u6839 \u2234x1²\uff1d\uff0d3x1\uff0d1\uff0c \u600e\u4e48\u7b97\u51fax1²\u7684\u5440\uff1f\uff1f\uff1f\u5148\u7528\u516c\u5f0f\u6cd5\u6c42\u51fa\u89e3\uff0c\u518d\u5c06\u89e3\u5e73\u65b9\u3002ok
\u89e3\uff1a\u7531\u9898\u610f\u53ef\u5f97\uff1a
x1+x2=3,x1*x2=-2
\u6240\u4ee5(x1+2)(x2+2)=x1*x2+2(x1+x2)+4=8
∴x2²-3x2+1=0
∴x2²=3x2-1
∴原式=3(x2+x1)-6
=3×3-6
=3
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x2^2-3x2+1=0
x2^2=3x2-1
x1+x2=3
原式=3x2-1+3x1-5=3(x1+x2)-6=3
5或23
因为X=1h或2•所以带进去就可以了
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