shmily呆
幼苗
共回答了18个问题采纳率:94.4% 举报
令t=x+1/x,则x²+1/x²=t²-2,原式:2(t²-2)-3t-1=0 即2t²-3t-5=0,解得t=3或者-1/2 即x+1/x=3或x+1/x=-1/2
而x+1/x=5/2,化简得2x²-5x+2=0 即(x-2)(2x-1)=0,解得x=2或1/2
x+1/x=-1化简得x²+x+1=0无解
综上:x=2或1/2
1年前
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shmily呆
3X^2+5XY-2Y^2+X+9Y-4 =(x+2y)(3x-y)+x+9y-4 =(x+2y)(3x-y)+(4x+8y-3x+y)-4 =(x+2y)(3x-y)+4(x+2y)-(3x-y)-4 =(x+2y)(3x-y) -(3x-y)+4(x+2y) -4 =(x+2y-1)(3x-y)+4(x+2y-1) =(x+2y-1)(3x-y+4)