shangzuojiang
幼苗
共回答了18个问题采纳率:77.8% 举报
(1) x1,x2为方程4kx²-4kx+k+1=0的两个根
则x1+x2=1, x1x2=(k+1)/(4k)
2(2x1-x2)(x1-2x2)+3=0 => 2[2x1²+2x2²-5x1x2]=2[2(x1+x2)²-9x1x2]+3=0
=> 2[2-9(k+1)/(4k)]+3=0 => k=9/5
∴存在k=9/5使方程成立
(2) x1/x2+x2/x1=(x1²+x2²)/(x1x2)=[(x1+x2)²-4x1x2]/(x1x2)
=(1-4x1x2)/(x1x2)=1/(x1x2)-4=4k/(k+1)-4=-4/(k+1)
欲使上述式子为整数,则-4/(k+1)必为整数
∴k+1必为4的约数,易知,k取整数时,有 k+1=±1,±2,±4;
∴满足条件的k的取值有:k=-5,-3,-2,0,1,3
1年前
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